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                                                                    EXHIBIT 10.6


                              EMPLOYMENT AGREEMENT

         This Employment Agreement ("Agreement") is made and entered into on
this 10th day of March, 2000, effective as of the date set forth in paragraph
2.1 below, and is by and between Terremark Holdings, Inc., a Florida corporation
(the "Company"), and Manuel D. Medina (hereinafter called the "Executive").

                                    RECITALS

         A. The Executive possesses knowledge and skills which the Company
believes will be of substantial benefit to its operations and success, and the
Company desires to employ the Executive on the terms and conditions set forth
below.

         B. The Executive is willing to make his services available to the
Company on the terms and conditions set forth below.

                                    AGREEMENT

         NOW, THEREFORE, in consideration of the premises and mutual covenants
set forth herein, the parties agree as follows:

         1.       EMPLOYMENT.

                  1.1      EMPLOYMENT AND TERM. The Company hereby agrees to
employ the Executive and the Executive hereby agrees to serve the Company on the
terms and conditions set forth herein.

                  1.2      DUTIES OF EXECUTIVE. During the Term of Employment
under this Agreement, the Executive shall serve as the President and Chairman of
Terremark Worldwide, Inc., shall diligently perform all services as may be
assigned to him by the Board (provided that, such services shall not materially
differ from the services currently provided by the Executive), and shall
exercise such power and authority as may from time to time be delegated to him
by the Board. The Executive shall devote his full time and attention to the
business and affairs of the Company, render such services to the best of his
ability, and use his best efforts to promote the interests of the Company. It
shall not be a violation of this Agreement for the Executive to (i) serve on
corporate, civic or charitable boards or committees, (ii) deliver lectures,
fulfill speaking engagements or teach at educational institutions, or (iii)
manage personal investments, so long as such activities do not significantly
interfere with the performance of the Executive's responsibilities to the
Company in accordance with this Agreement.

         2.       TERM.

                  2.1      INITIAL TERM. The initial Term of Employment under
this Agreement, and the employment of the Executive hereunder, shall commence on
the date on which the pending merger of the Company into AmTec, Inc. becomes
effective (the "Commencement Date") and




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shall expire on the date that is twelve months after the Commencement Date,
unless sooner terminated in accordance with Section 5 hereof (the "Initial
Term"). In the event the merger of the Company into AmTec, Inc. has not closed
by December 31, 2000, the Agreement shall be void.

                  2.2      RENEWAL TERMS. At the end of the Initial Term, the
Term of Employment automatically shall renew for successive one year terms
(subject to earlier termination as provided in Section 5 hereof), unless the
Company or the Executive delivers written notice to the other at least one month
prior to the Expiration Date of its or his election not to renew the Term of
Employment.

                  2.3      TERM OF EMPLOYMENT AND EXPIRATION DATE. The period
during which the Executive shall be employed by the Company pursuant to the
terms of this Agreement is sometimes referred to in this Agreement as the "Term
of Employment", and the date on which the Term of Employment shall expire
(including the date on which any renewal term shall expire), is sometimes
referred to in this Agreement as the "Expiration Date".

         3.       COMPENSATION.

                  3.1      BASE SALARY. The Executive shall receive a base
salary at the annual rate of $350,000.00 (the "Base Salary") during the Term of
Employment, with such Base Salary payable in installments consistent with the
Company's normal payroll schedule, subject to applicable withholding and other
taxes. The Base Salary shall be reviewed, at least annually, for merit
increases and may, by action and in the sole discretion of the Board, be
increased at any time or from time to time.

                  3.2.     BONUSES. During the Term of Employment, the
Executive shall be eligible to receive bonuses in such amounts and at such
times as the Board shall determine in its sole discretion.

         4.       EXPENSE REIMBURSEMENT AND OTHER BENEFITS.

                  4.1      REIMBURSEMENT OF EXPENSES. Upon the submission of
proper substantiation by the Executive, and subject to such rules and
guidelines as the Company may from time to time adopt, the Company shall
reimburse the Executive for all reasonable expenses actually paid or incurred
by the Executive during the Term of Employment in the course of and pursuant to
the business of the Company. The Executive shall account to the Company in
writing for all expenses for which reimbursement is sought and shall supply to
the Company copies of all relevant invoices, receipts or other evidence
reasonably requested by the Company.

                  4.2      COMPENSATION/BENEFIT PROGRAMS. During the term of
Employment, the Executive shall be entitled to participate in all medical,
dental, hospitalization, accidental death and dismemberment, disability, travel
and live insurance plans, and any and all other plans as are presently and
hereinafter offered by the Company to its executives, including savings,
pension, profit-sharing and deferred compensation plans, subject to the general
eligibility and participation provisions set forth in such plans.


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                  4.3      WORKING FACILITIES. During the Term of Employment,
the Company shall furnish the Executive with an office, secretarial help and
such other facilities and services suitable to his/her position and adequate
for the performance of his/her duties hereunder.

                  4.4      STOCK OPTIONS. During the Term of Employment, the
Executive shall be eligible to be granted options (the "Stock Options") to
purchase common stock (the "Common Stock") of the Company under (and therefore
subject to all terms and conditions of) the Company's 1996 Stock Option Plan,
as amended, and any successor plan thereto (the "Stock Option Plan") and all
rules of regulation of the Securities and Exchange Commission applicable to
stock option plans then in effect. The number of Stock Options and terms and
conditions of the Stock Options shall be determined by the Committee appointed
pursuant to the Stock Option Plan, or by the Board of Directors of the Company,
in its sole discretion and pursuant to the Stock Option Plan.

                  4.5      OTHER BENEFITS. The Executive shall be entitled to
three weeks of vacation each calendar year during the Term of Employment, to be
taken at such times as the Executive and the Company shall mutually determine
and provided that no vacation time shall interfere with the duties required to
be rendered by the Executive hereunder. Any vacation time not taken by
Executive during any calendar year may not be carried forward into any
succeeding calendar year. The Executive shall receive such additional benefits,
if any, as the Board of the Company shall from time to time determine.

         5.       TERMINATION.

                  5.1      TERMINATION FOR CAUSE. The Company shall at all
times have the right, upon written notice to the Executive, to terminate the
Term of Employment, for Cause. For purposes of this Agreement, the term "Cause"
shall mean (i) an action or omission of the Executive which constitutes a
willful and material breach of, or failure or refusal (other than by reason of
his disability) to perform his duties under, this Agreement which is not cured
within fifteen (15) days after receipt by the Executive of written notice of
same, (ii) fraud, embezzlement, misappropriation of funds or breach of trust in
connection with his services hereunder, (iii) conviction of a felony or any
other crime which involves dishonesty or a breach of trust, or (iv) gross
negligence in connection with the performance of the Executive's duties
hereunder, which is not cured within fifteen (15) days after written receipt by
the Executive of written notice of same. Any termination for Cause shall be
made in writing to the Executive, which notice shall set forth in detail all
acts or omissions upon which the Company is relying for such termination. The
Executive shall have the right to address the Board regarding the acts set
forth in the notice of termination. Upon any termination pursuant to this
Section 5.1, the Company shall only be obligated to pay to the Executive his
Base Salary to the date of termination. The Company shall have no further
liability hereunder (other than for reimbursement for reasonable business
expenses incurred prior to the date of termination, subject, however, to the
provisions of Section 4.1.

                  5.2      DISABILITY. The Company shall at all times have the
right, upon written notice to the Executive, to terminate the Term of
Employment, if the Executive shall become entitled to benefits under the
Company's group disability policy or any individual disability policy then in
effect, or, if the Executive shall as the result of mental or physical
incapacity, illness or


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disability, become unable to perform his obligations hereunder for a period of
90 days in any 12-month period. The Company shall have sole discretion based
upon competent medical advice to determine whether the Executive continues to
be disabled. Upon any termination pursuant to this Section 5.2, the Company
shall (i) pay to the Executive any unpaid Base Salary through the effective
date of termination specified in such notice, (ii) pay to the Executive a
severance payment equal to one month of the Executive's Base Salary at the time
of the termination of the Executive's employment with the Company. The Company
shall have no further liability hereunder (other than for reimbursement for
reasonable business expenses incurred prior to the date of termination,
subject, however to the provisions of Section 4.1).

                  5.3      DEATH. Upon the death of the Executive during the
Term of Employment, the Company shall pay to the estate of the deceased
Executive any unpaid Base Salary through the Executive's date of death. The
Company shall have no further liability hereunder (other than for reimbursement
for reasonable business expenses incurred prior to the date of the Executive's
death, subject, however, to the provisions of Section 4.1).

                  5.4      TERMINATION WITHOUT CAUSE. At any time the Company
shall have the right to terminate the Term of Employment by written notice to
the Executive. Upon any termination pursuant to this Section 5.4 (that is not a
termination under any of Sections 5.1, 5.2, 5.3, 5.5 or 5.6), the Company shall
(i) pay to the Executive any unpaid Base Salary through the effective date of
termination specified in such notice, (ii) continue to pay the Executive's Base
Salary for a period (the "Continuation Period") through the date on which the
Term of Employment would have ended pursuant to Section 2 hereof in the absence
of an earlier termination pursuant to this Section 5 but in no event for more
than six (6) months from notice of termination hereunder, (iii) continue to
provide the Executive with the benefits he/she was receiving under Sections 4.2
and 4.4 hereof (the "Benefits") through the end of the Continuation Period in
the manner and at such times as the Incentive Compensation or Benefits
otherwise would have been payable or provided to the Executive. In the event
that the Company is unable to provide the Executive with any Benefits required
hereunder by reason of the termination of the Executive's employment pursuant
to this Section 5.4, then the Company shall pay the Executive cash equal to the
value of the Benefit that otherwise would have accrued for the Executive's
benefit under the plan, for the period during which such Benefits could not be
provided under the plans. The Company's good faith determination of the amount
that would have been contributed or the value of any Benefits that would have
accrued under any plan shall be binding and conclusive on the Executive. For
this purpose, the Company may use as the value of any Benefit the cost to the
Company of providing that Benefit to the Executive. Further, the Executive
shall continue to vest in the Executive's Stock Options through the end of the
Continuation Period in the same manner and to the same extent as if his
employment hereunder terminated on the last day of the Continuation Period. The
Company shall have no further liability hereunder (other than for (x)
reimbursement for reasonable business expenses incurred prior to the date of
termination, subject, however, to the provisions of Section 4.1, and (y)
payment of compensation for unused vacation days that have accumulated during
the calendar year in which such termination occurs).

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                  5.5      TERMINATION BY EXECUTIVE.

                           (a)      The Executive shall at all times have the
right, upon sixty (60) days written notice to the Company, to terminate the
Term of Employment.

                           (b)      Upon termination of the Term of Employment
pursuant to this Section 5.5 (that is not a termination under Section 5.6) by
the Executive without Good Reason, the Company shall pay to the Executive any
unpaid Base Salary through the effective date of termination specified in such
notice. The Company shall have no further liability hereunder (other than for
reimbursement for reasonable business expenses incurred prior to the date of
termination, subject, however, to the provisions of Section 4.1). At the
Company's sole option, upon receipt of notice from the Executive pursuant to
this Section, the Company may immediately terminate the Term of Employment, in
which case, in addition to the covenants set forth above, the Company shall pay
the Executive 60 days of Base Salary.

                           (c)      Upon termination of the Term of Employment
pursuant to this Section 5.5 (that is not a termination under Section 5.6) by
the Executive for Good Reason, the Company shall pay to the Executive the same
amounts that would have been payable by the Company to the Executive under
Section 5.4 of this Agreement if the Term of Employment had been terminated by
the Company without Cause. The Company shall have no further liability
hereunder.

                           (d)      For purposes of this Agreement, "Good
Reason" shall mean (i) the assignment to the Executive of any duties
inconsistent in any respect with the Executive's position (including status,
offices, titles and reporting requirements), authority, duties or
responsibilities as contemplated by Section 1.2 of this Agreement, or any other
action by the Company which results in a diminution in such position,
authority, duties or responsibilities, excluding for this purpose an isolated,
insubstantial and inadvertent action not taken in bad faith and which is
remedied by the Company promptly after receipt of notice thereof given by the
Executive; (ii) any failure by the Company to comply with any of the provisions
of Article 3 of this Agreement, other than an isolated, insubstantial and
inadvertent failure not occurring in bad faith and which is remedied by the
Company promptly after receipt of notice thereof given by the Executive; (iii)
the Company's requiring the Executive to be based at any office or location
outside of the area for which Executive was originally hired to work except for
travel reasonably required in the performance of the Executive's
responsibilities. For purposes of this Section 5.5(d), any good faith
determination of "Good Reason" made by the Board shall be conclusive.

                  5.6      CHANGE IN CONTROL OF THE COMPANY.

                           (a)      In the event that (i) a Change in Control
(as defined in paragraph (b) of this Section 5.6) in the Company shall occur
during the Term of Employment, and (ii) prior to the later of the Expiration
Date or one year after the date of the Change in Control, either (x) the Term
of Employment is terminated by the Company without Cause, pursuant to Section
5.4 hereof or (y) the Executive terminates the Term of Employment for Good
Reason the Company shall (1) pay to the Executive any unpaid Base Salary
through the effective date of termination, (2) pay to the Executive as a single
lump sum payment, within 30 days of the termination of his


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employment hereunder, a lump sum payment equal to the sum of (x) two times the
sum of Executive's annual Base Salary, Incentive Compensation, and the value of
the annual fringe benefits (based upon their cost to the Company) required to
be provided to the Executive under Sections 4.2 and 4.4 hereof, for the year
immediately preceding the year in which his employment terminates, plus (y)
the value of the portion of his benefits under any savings, pension, profit
sharing or deferred compensation plans that are forfeited under those plans by
reason of the termination of his employment hereunder. Further, upon the Change
in Control, the Executive's Stock Options shall immediately vest. The Company
shall have no further liability hereunder (other than for (1) reimbursement for
reasonable business expenses incurred prior to the date of termination,
subject, however, to the provisions of Section 4.1, and (2) payment of
compensation for unused vacation days that have accumulated during the calendar
year in which such termination occurs).

                           (b)      For purposes of this Agreement, the term
"Change in Control" shall mean:

                                    (i)      Approval by the shareholders of
the Company of (x) a reorganization, merger, consolidation or other form of
corporate transaction or series of transactions, in each case, with respect to
which persons who were the shareholders of the Company immediately prior to
such reorganization, merger or consolidation or other transaction do not,
immediately thereafter, own more than 50% of the combined voting power entitled
to vote generally in the election of directors of the reorganized, merged or
consolidated company's then outstanding voting securities, in substantially the
same proportions as their ownership immediately prior to such reorganization,
merger, consolidation or other transaction, or (y) a liquidation or
dissolution of the Company or (z) the sale of all or substantially all of the
assets of the Company (unless such reorganization, merger, consolidation or
other corporate transaction, liquidation, dissolution or sale is subsequently
abandoned);

                                    (ii)     the acquisition (other than from
the Company) by any person, entity or "group", within the meaning of
Section 13(d)(3) or 14(d)(2) of the Securities Exchange Act, of more than 30%
of either the then outstanding shares of the Company's Common Stock or the
combined voting power of the Company's then outstanding voting securities
entitled to vote generally in the election of directors (hereinafter referred
to as the ownership of a "Controlling Interest") excluding, for this purpose,
any acquisitions by (1) the Company or its Subsidiaries, (2) any person, entity
or "group" that as of the Commencement Date of this Agreement owns beneficial
ownership (within the meaning of Rule 13d-3 promulgated under the Securities
Exchange Act) of a Controlling Interest or (3) any employee benefit plan of the
Company or its Subsidiaries.

                                    (iii)    The resignation of Manuel D.
Medina as both Chairman and CEO of the Company, his death, or his absence from
the day to day business affairs of the Company for more than 90 consecutive
days due to disability or incapacity.

                  5.7      RESIGNATION.      Upon any notice or termination of
employment pursuant to this Article 5, the Executive shall automatically and
without further action be deemed to have resigned as an officer, and if he or
she was then serving as a director of the Company, as a

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director, and if required by the Board, the Executive hereby agrees to
immediately execute a resignation letter to the Board.

                  5.8      SURVIVAL.  The provisions of this Article 5
shall survive the termination of this Agreement, as applicable.

         6.       RESTRICTIVE COVENANTS.

                  6.1      NON-COMPETITION.  At all times while the Executive
is employed by the Company and for a one year period after the termination of
the Executive's employment with the Company for any reason (other than by the
Company without Cause (as defined in Section 5.1 hereof) or by the Executive for
Good Reason (as defined in Section 5.5(d) hereof)), the Executive shall not,
directly or indirectly, engage in or have any interest in any sole
proprietorship, partnership, corporation or business or any other person or
entity (whether as an employee, officer, director, partner, agent, security
holder, creditor, consultant or otherwise) that directly or indirectly (or
through any affiliated entity) engages in competition with the Company (based on
the business in which the Company was engaged or was actively planning on being
engaged as of the date of termination of the Employee's employment and in the
geographic areas in which the Company operated or was actively planning on
operating as of date of termination of the Employee's employment); provided that
such provision shall not apply to the Executive's ownership of Common Stock of
the Company or the acquisition by the Executive, solely as an investment, of
securities of any issuer that is registered under Section 12(b) or 12(g) of the
Securities Exchange Act of 1934, as amended, and that are listed or admitted for
trading on any United States national securities exchange or that are quoted on
the National Association of Securities Dealers Automated Quotations System, or
any similar system or automated dissemination of quotations of securities prices
in common use, so long as the Executive does not control, acquire a controlling
interest in or become a member of a group which exercises direct or indirect
control or, more than five percent of any class of capital stock of such
corporation.

                  6.2      NONDISCLOSURE. The Executive shall not at any time
divulge, communicate, use to the detriment of the Company or for the benefit of
any other person or persons, or misuse in any way, any Confidential Information
(as hereinafter defined) pertaining to the business of the Company. Any
Confidential Information or data now or hereafter acquired by the Executive with
respect to the business of the Company (which shall include, but not be limited
to, information concerning the Company's financial condition, prospects,
technology, customers, suppliers, sources of leads and methods of doing
business) shall be deemed a valuable, special and unique asset of the Company
that is received by the Executive in confidence and as a fiduciary, and
Executive shall remain a fiduciary to the Company with respect to all of such
information. For purposes of this Agreement, "Confidential Information" means
information disclosed to the Executive or known by the Executive as a
consequence of or through his employment by the Company (including information
conceived, originated, discovered or developed by the Executive) prior to or
after the date hereof, and not generally known, about the Company or its
business. Notwithstanding the foregoing, nothing herein shall be deemed to
restrict the Executive from disclosing Confidential Information to the extent
required by law.


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                  6.3      NONSOLICITATION OF EMPLOYEES AND CLIENTS. At all
times while the Executive is employed by the Company and for a two (2) year
period after the termination of the Executive's employment with the Company for
any reason, the Executive shall not, directly or indirectly, for himself or for
any other person, firm, corporation, partnership, association or other entity
(a) employ or attempt to employ or enter into any contractual arrangement with
any employee or former employee of the Company, unless such employee or former
employee has not been employed by the Company for a period in excess of six
months, and/or (b) call on or solicit any of the actual or targeted prospective
clients of the Company on behalf of any person or entity in connection with any
business competitive with the business of the Company, nor shall the Executive
make known the names and addresses of such clients or any information relating
in any manner to the Company's trade or business relationships with such
customers, other than in connection with the performance of Executive's duties
under this Agreement.

                  6.4      OWNERSHIP OF DEVELOPMENTS. All copyrights, patents,
trade secrets, or other intellectual property rights associated with any ideas,
concepts, techniques, inventions, processes, or works of authorship developed
or created by Executive during the course of performing work for the Company or
its clients (collectively, the "Work Product") shall belong exclusively to the
Company and shall, to the extent possible, be considered a work made by the
Executive for hire for the Company within the meaning of Title 17 of the United
States Code. To the extent the Work Product may not be considered work made by
the Executive for hire for the Company, the Executive agrees to assign, and
automatically assign at the time of creation of the Work Product, without any
requirement of further consideration, any right, title, or interest the
Executive may have in such Work Product. Upon the request of the Company, the
Executive shall take such further actions, including execution and delivery of
instruments of conveyance, as may be appropriate to give full and proper effect
to such assignment.

                  6.5      BOOKS AND RECORDS. All books, records, and accounts
relating in any manner to the customers or clients of the Company, whether
prepared by the Executive or otherwise coming into the Executive's possession,
shall be the exclusive property of the Company and shall be returned
immediately to the Company on termination of the Executive's employment
hereunder or on the Company's request at any time.

                  6.6      DEFINITION OF COMPANY. Solely for purposes of this
Article 6, the term "Company" also shall include any existing or future
subsidiaries of the Company that are operating during the time periods
described herein and any other entities that directly or indirectly, through
one or more intermediaries, control, are controlled by or are under common
control with the Company during the periods described herein.

                  6.7      ACKNOWLEDGEMENT BY EXECUTIVE. The Executive
acknowledges and confirms that (a) the restrictive covenants contained in this
Article 6 are reasonably necessary to protect the legitimate business interests
of the Company, and (b) the restrictions contained in this Article 6 (including
without limitation the length of the term of the provisions of this Article 6)
are not overbroad, overlong, or unfair and are not the result of overreaching,
duress or coercion of any kind. The Executive further acknowledges and confirms
that his full, uninhibited and faithful observance of each of the covenants
contained in this Article 6 will not cause him any undue hardship, financial or
otherwise, and that enforcement of each of the covenants contained herein


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<PAGE>   9
will not impair his ability to obtain employment commensurate with his abilities
and on terms fully acceptable to him or otherwise to obtain income required for
the comfortable support of him and his family and the satisfaction of the needs
of his creditors. The Executive acknowledges and confirms that his special
knowledge of the business of the Company is such as would cause the Company
serious injury or loss if he were to use such ability and knowledge to the
benefit of a competitor or were to compete with the Company in violation of the
terms of this Article 6. The Executive further acknowledges that the
restrictions contained in this Article 6 are intended to be, and shall be, for
the benefit of and shall be enforceable by, the Company's successors and
assigns.

                  6.8      REFORMATION BY COURT. In the event that a court of
competent jurisdiction shall determine that any provision of this Article 6 is
invalid or more restrictive than permitted under the governing law of such
jurisdiction, then only as to enforcement of this Article 6 within the
jurisdiction of such court, such provision shall be interpreted and enforced as
if it provided for the maximum restriction permitted under such governing law.

                  6.9      EXTENSION OF TIME. If the Executive shall be in
violation of any provision of this Article 6, then each time limitation set
forth in this Article 6 shall be extended for a period of time equal to the
period of time during which such violation or violations occur. If the Company
seeks injunctive relief from such violation in any court, then the covenants
set forth in this Article 6 shall be extended for a period of time equal to the
pendency of such proceeding including all appeals by the Executive.

                  6.10     SURVIVAL. The provisions of this Article 6 shall
survive the termination of this Agreement, as applicable.

         7.       INJUNCTION. It is recognized and hereby acknowledged by the
parties hereto that a breach by the Executive of any of the covenants contained
in Article 6 of this Agreement will cause irreparable harm and damage to the
Company, the monetary amount of which may be virtually impossible to ascertain.
As a result, the Executive recognizes and hereby acknowledges that the Company
shall be entitled to an injunction from any court of competent jurisdiction
enjoining and restraining any violation of any or all of the covenants
contained in Article 6 of this Agreement by the Executive or any of his
affiliates, associates, partners or agents, either directly or indirectly, and
that such right to injunction shall be cumulative and in addition to whatever
other remedies the Company may possess.

         8.       ASSIGNMENT. Neither party shall have the right to assign or
delegate his rights or obligations hereunder, or any portion thereof, to any
other person.

         9.       GOVERNING LAW. This Agreement shall be governed by and
construed in accordance with the laws of the State of Florida.

         10.      SECTION 162(m) LIMITS. Notwithstanding any other provision of
this Agreement to the contrary, if and to the extent that any remuneration
payable by the Company to the Executive for any year would exceed the maximum
amount of remuneration that the Company may deduct for that year under Section
162(m) ("Section 162(m)") of the Internal Revenue Code of 1986, as amended (the
"Code"), payment of the portion of the remuneration for that year that


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<PAGE>   10
would not be so deductible under Section 162(m) shall, in the sole discretion
of the Board, be deferred and become payable at such time or times as the Board
determines that it first would be deductible by the Company under Section
162(m), with interest at the "short-term applicable rate" as such term is
defined in section 1274(d) of the Code. The limitation set forth under this
Section 10 shall not apply with respect to any amounts payable to the
Executive pursuant to Article 5 hereof.

         11.      ENTIRE AGREEMENT. This Agreement constitutes the entire
agreement between the parties hereto with respect to the subject matter hereof
and, upon its effectiveness, shall supersede all prior agreements,
understandings and arrangements, both oral and written, between the Executive
and the Company (or any of its affiliates) with respect to such subject matter.
This Agreement may not be modified in any way unless by a written instrument
signed by both the Company and the Executive.

         12.      NOTICES. All notices required or permitted to be given
hereunder shall be in writing and shall be personally delivered by courier,
sent by registered or certified mail, return receipt requested or sent by
confirmed facsimile transmission addressed as set forth herein. Notices
personally delivered, sent by facsimile or sent by overnight courier shall be
deemed given on the date of delivery and notices mailed in accordance with the
foregoing shall be deemed given upon the earlier of receipt by the addressee,
as evidenced by the return receipt thereof, or three (3) days after deposit in
the U.S. mail. Notice shall be sent (i) if to the Company, addressed to
Terremark.com, Inc., 2601 S. Bayshore Drive, 9th Floor, Miami, Florida 33133,
Attn: Brian K. Goodkind, Executive Vice-President, and (ii) if to the
Executive, to his address as reflected on the payroll records of the Company,
or to such other address as either party hereto may from time to time give
notice of to the other.

         13.      BENEFITS; BINDING EFFECT. This Agreement shall be for the
benefit of and binding upon the parties hereto and their respective heirs,
personal representatives, legal representatives, successors and, where
applicable, assigns, including, without limitation, any successor to the
Company, whether by merger, consolidation, sale of stock, sale of assets or
otherwise. Specifically, this Agreement shall be binding upon the survivor of
the Merger of the Company into AmTec, Inc.

         14.      SEVERABILITY. The invalidity of any one or more of the words,
phrases, sentences, clauses or sections contained in this Agreement shall not
affect the enforceability of the remaining portions of this Agreement or any
part thereof, all of which are inserted conditionally on their being valid in
law, and, in the event that any one or more of the words, phrases, sentences,
clauses or sections contained in this Agreement shall be declared invalid, this
Agreement shall be construed as if such invalid word or words, phrase or
phrases, sentence or sentences, clause or clauses, or section or sections had
not been inserted. If such invalidity is caused by length of time or size of
area, or both, the otherwise invalid provision will be considered to be reduced
to a period or area which would cure such invalidity.

         15.      WAIVERS. The waiver by either party hereto of a breach or
violation of any term or provision of this Agreement shall not operate nor be
construed as a waiver of any subsequent breach or violation.


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         16.      DAMAGES. Nothing contained herein shall be construed to
prevent the Company or the Executive from seeking and recovering from the other
damages sustained by either or both of them as a result of its or his breach of
any term or provision of this Agreement. In the event that either party hereto
brings suit for the collection of any damages resulting from, or the injunction
of any action constituting, a breach of any of the terms or provisions of this
Agreement, then the party found to be at fault shall pay all reasonable court
costs and attorneys' fees of the other.

         17.      SECTION HEADINGS. The section headings contained in this
Agreement are for reference purposes only and shall not affect in any way the
meaning or interpretation of this Agreement.

         18.      NO THIRD PARTY BENEFICIARY. Nothing expressed or implied in
this Agreement is intended, or shall be construed, to confer upon or give any
person other than the Company, the parties hereto and their respective heirs,
personal representatives, legal representatives, successors and assigns, any
rights or remedies under or by reason of this Agreement.

         19.      INDEMNIFICATION.

                           (a)      Subject to limitations imposed by law, the
Company shall indemnify and hold harmless the Executive to the fullest extent
permitted by law from and against any and all claims, damages, expenses
(including attorneys' fees), judgments, penalties, fines, settlements, and all
other liabilities incurred or paid by him in connection with the investigation,
defense, prosecution, settlement or appeal of any threatened, pending or
completed action, suit or proceeding, whether civil, criminal, administrative
or investigative and to which the Executive was or is a party or is threatened
to be made a party by reason of the fact that the Executive is or was an
officer, employee or agent of the Company, or by reason of anything done or not
done by the Executive in any such capacity or capacities, provided that the
Executive acted in good faith, in a manner that was not grossly negligent or
constituted willful misconduct and in a manner he reasonably believed to be in
or not opposed to the best interests of the Company, and, with respect to any
criminal action or proceeding, had no reasonable cause to believe his conduct
was unlawful. The Company also shall pay any and all expenses (including
attorney's fees) incurred by the Executive as a result of the Executive being
called as a witness in connection with any matter involving the Company and/or
any of its officers or directors.

                           (b)      The Company shall pay any expenses
(including attorneys' fees), judgments, penalties, fines, settlements, and
other liabilities incurred by the Executive in investigating, defending,
settling or appealing any action, suit or proceeding described in this
Section 19 in advance of the final disposition of such action, suit or
proceeding. The Company shall promptly pay the amount of such expenses to the
Executive, but in no event later than 10 days following the Executive's
delivery to the Company of a written request for an advance pursuant to this
Section 19, together with a reasonable accounting of such expenses.

                           (c)      The Executive hereby undertakes and agrees
to repay to the Company any advances made pursuant to this Section 19 if and to
the extent that it shall


                                      -11-
<PAGE>   12
ultimately be found that the Executive is not entitled to be indemnified by the
Company for such amounts.

                           (d)      The Company shall make the advances
contemplated by this Section 19 regardless of the Executive's financial ability
to make repayment, and regardless whether indemnification of the Indemnitee by
the Company will ultimately be required. Any advances and undertakings to repay
pursuant to this Section 19 shall be unsecured and interest-free.

                           (e)      The provisions of this Section 19 shall
survive the termination of this Agreement.

         IN WITNESS WHEREOF, the undersigned have executed this Agreement as of
the date first above written.



                                             COMPANY:

                                             TERREMARK HOLDINGS, INC.

                                             By: /s/ Brian K. Goodkind
                                                 -------------------------------
                                             Name: Brian K. Goodkind
                                             Title: Executive Vice-President


                                             EXECUTIVE:


                                             /s/ Manuel D. Medina
                                             -----------------------------------
                                             Name: Manuel D. Medina



                                      -12-
<PAGE>   13
By its acknowledgment below, the undersigned the Employment Agreement that was
executed between the undersigned and Terremark Holdings, Inc. shall be amended
as follows:

1.       The following provision shall be added to the end of Section 5.4: "For
         all purposes hereunder, the failure by Company to offer to renew the
         Agreement following the expiration of the Initial Term or any Renewal
         Term on the same terms and conditions hereunder shall be treated as if
         the Company terminated this Agreement pursuant to this Section 5.4."

2.       The following provision shall be added to the end of Section 5.5(b):
         "For all purposes hereunder, the failure by Executive to offer to renew
         the Agreement following the expiration of the Initial Term or any
         Renewal Term on the same terms and conditions hereunder shall be
         treated as if the Executive terminated this Agreement pursuant to this
         Section 5.5, except that the Executive shall not be entitled to any
         Base Salary in excess of that which is due through the last day of
         Executive's employment hereunder."


Terremark Holdings, Inc.                     Executive:

By: /s/ Brian K. Goodkind                    /s/ Manuel D. Medina
    ----------------------------             -----------------------------
Name: Brian K. Goodkind                      Print Name: Maneul D. Medina
Title: Executive Vice-President