FOURTH AMENDMENT TO LEASE



         THIS FOURTH  AMENDMENT TO LEASE (the  "Amendment")  is made and entered
into this  ______ day of , 1996,  by and between  LAFP-SF,  Inc.,  successor  in
interest to The Prudential Insurance Company Of America ("Landlord"),  having an
office c/o Lowe Enterprises  Colorado,  Inc., 1475 Lawrence  Street,  Suite 210,
Denver,  Colorado 80202, and Data Transmission  Network Corporation  ("Tenant"),
having an office at 9110 West Dodge Road, Suite 200, Omaha, Nebraska 68114.


                                    RECITALS

A.       The  Prudential  Insurance  Company  of America  and Data  Transmission
         Network  Corporation entered into that certain Lease dated as of May 2,
         1995, for Suites #175A, #110, #200, #300, #301, #310, #320, #325, #340,
         #360, and #362  containing  75,931 rentable square feet in the Building
         known as  Embassy  Plaza,  located  at 9110  West  Dodge  Road,  Omaha,
         Nebraska ("the Premises").

B.       Subsequently,  The  Prudential  Insurance  Company Of America  and Data
         Transmission  Network  Corporation  executed a First Amendment To Lease
         dated  September 29, 1995, a Second  Amendment To Lease dated  November
         30, 1995,  and a Third  Amendment To Lease dated  January 5, 1996.  The
         combined terms of the Lease and subsequent  Amendments  shall herein be
         referred to as the "Lease".  Under the Lease the Premises consists of a
         total of 83,284 RSF.

C.       All  capitalized  terms not  defined  herein  shall  have the  meanings
         ascribed to them in the Lease.

         NOW,  THEREFORE,  in consideration of the foregoing  promises and other
good and  valuable  considerations,  the  receipt and  sufficiency  of which are
hereby acknowledged, the parties hereto covenant and agree as follows:

1.       Premises.  Effective January 1, 1997, the Premises shall be expanded to
         include Suite 350A, measuring 3,348 RSF; Suite 350B, measuring 710 RSF;
         and the  contiguous  corridor  area,  measuring 794 RSF; for a total of
         4,852 RSF as shown on the floor plan attached  hereto,  marked  Exhibit
         "A" (the "Additional  Space") and by this reference made a part hereof.
         Notwithstanding  the above,  both Tenant and Landlord  understand  that
         Travelers Insurance Company currently leases Suite 350A and Suite 350B,
         with such lease expiring December 31, 1996.  Should Travelers  holdover
         and not vacate  Suites 350A  and/or  350B by January 1, 1997,  Landlord
         will make  reasonable  efforts  to pursue  its legal  remedies  to have
         Travelers  removed from the space. If the Additional Space is delivered
         to Tenant after  January 1, 1997,  Landlord and Tenant shall  execute a
         Commencement  Date  Certificate in the form attached  hereto as Exhibit
         "C",  confirming  Landlord's  delivery  of  the  Additional  Space  and
         commencement of the Lease with respect to the Additional Space.

2.       Term.  The term of the  Lease  with  respect  to the  Additional  Space
         identified  in Paragraph 1 above shall  commence  January 1, 1997,  and
         terminate upon termination of the Lease.



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3.       Base  Rent.  Tenant  shall  pay as Base Rent for the  Additional  Space
         during the Term the sum of Six Hundred and Two Thousand,  Three Hundred
         Fifty-five Dollars and Ninety-Two Cents  ($602,355.92)  payable monthly
         as follows:

         January 1, 1997 - May 31, 2005                $5,963.92 / Month

4.       Adjustment  Rent.  Effective  upon  commencement  of the  Term  for the
         Additional Space,  Tenant shall pay Adjustment Rent with respect to the
         Additional Space in accordance with the terms and conditions  contained
         in Paragraph 2 of the Lease.


5.       Tenant  Improvements.  Landlord  shall  provide  a  tenant  improvement
         allowance of up to $48,600.19 to be applied toward the cost of Tenant's
         required building improvements.  All improvements shall be performed in
         accordance with the Tenant  Improvement Work Schedule  attached hereto,
         marked as Exhibit "B", and by this reference made a part hereof.

6.       Tenant's  Proportionate  Share. The schedule of Tenant's  Proportionate
         Share  contained  in Item D of the Basic  Terms of the  Lease  shall be
         replaced with the following schedule:

        January 1, 1997 - December 31, 1997    59.13% (77,990 RSF / 131,888 RSF)
        January 1, 1998 - May 31, 2005         66.83% (88,136 RSF / 131,888 RSF)

7.       Effect of Agreement.  Except as herein specifically provided, the terms
         and conditions of the Lease shall continue in full force and effect

6.       This  Amendment  shall be binding  upon and inure to the benefit of the
         parties hereto, their successors and assigns.

7.       The  parties   hereto  hereby   reaffirm  and  ratify  all   covenants,
         representations  and  warranties  in  the  Lease  as  amended  by  this
         Amendment.

         IN WITNESS WHEREOF, Landlord and Tenant have executed this Amendment as
of the day and year first above written.


Tenant:                                         Landlord:

Data Transmission Network Corporation,          LAFP-SF, Inc.
a Delaware corporation

                                                By:  Lowe Enterprises Investment
                                                     Management, Inc.
By:                                             Its:  Authorized Agent


Its:                                            By:


                                                Its:





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EXHIBIT "B" to be made a part of a Fourth  Amendment To Lease  between  LAFP-SF,
INC.  (Landlord),  and DATA TRANSMISSION NETWORK CORPORATION  (Tenant),  dated ,
1996. (Page 1 of 2)



                        TENANT IMPROVEMENTS WORK SCHEDULE



                                    ARTICLE I
                       Landlord's Construction Obligations

     Landlord  shall have no  construction  obligations  under  this  Amendment.
Tenant accepts the Additional Premises in an "as is" condition,  with all faults
and  with  the  understanding  that  it  shall  be  responsible  for any and all
improvements required for its occupancy and use in accordance with Article II of
this Exhibit "B".



                                   ARTICLE II
                       Construction of Tenant Improvements

     Tenant  shall  have the right to place  partitions  and  fixtures  and make
improvements or other alterations in the Additional Space in accordance with the
provisions of Paragraph 9 of the Lease.  Landlord  shall provide Tenant a tenant
finish allowance of up to Forty Eight Thousand, Six Hundred Dollars and Nineteen
Cents  ($48,600.19)  to be applied  toward the cost of any such  tenant-provided
improvements as follows:

     1. The tenant finish allowance shall be paid in periodic installments,  not
more frequently than once per month,  equal to the total of the  contractor's or
consultant's  invoice  amounts for  improvements  made to the Additional  Space,
excluding   any   furnishings   or  business   equipment   (such  as  computers,
satellite/microwave  dish, office  equipment,  etc.), as submitted by Tenant and
verified to Landlord's  reasonable  satisfaction;  provided,  however, that such
payments  will be made only if Tenant is not then in Default  under the terms of
this Lease and invoices are  accompanied  by lien waivers in the amount equal to
that of the  invoices.  The  tenant  finish  allowance  shall be  allocated  and
distributed subject to the provisions of this Exhibit "B" as follows:

       January 1, 1997 - December 31, 1997                      Up To $48,600.19


     2. Upon the earlier of the end date  identified in the allocation  schedule
specified  in  Paragraph  1  above,  or  the  satisfaction  of  all  obligations
associated  with the  tenant  improvements  covered  under  this  Article II and
receipt of the  associated  lien waivers for the work,  the Tenant shall forfeit
any unused  portion of the allowance.  Any requests for payment  received by the
Landlord after the above specified end dates, will be returned to the Tenant and
will be the obligation and sole responsibility of the Tenant.



     3.       In  addition  to the  provisions  set forth in  Paragraph 9 of the
              Lease,  Tenant's  contractor  shall  (and  its  contract  shall so
              provide):

         (a)  conduct  its  work  in  such a  manner  so as not to  unreasonably
              interfere with other tenants in the Building, Building operations,
              or any other  construction  occurring on or in the Building or the
              Premises;

         (b)  execute  a set  of and  comply  with  all  rules  and  regulations
              relating to the  construction  activities in or on the Building as
              may be reasonably promulgated from time to time by Landlord or its
              agents;

         (c)  maintain such insurance  (such as general  liability and workman's
              compensation)  and bonds (such as performance  and  completion) in
              force and effect as may be reasonably  requested by Landlord or as
              required by  applicable  law (but in any event said bonds shall be
              in amounts  equal to the full value or cost of the work being done
              by the Tenant contractor);



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EXHIBIT "B" to be made a part of a Fourth  Amendment To Lease  between  LAFP-SF,
INC.  (Landlord),  and DATA TRANSMISSION NETWORK CORPORATION  (Tenant),  dated ,
1996. (Page 2 of 2)



         (d)  be  responsible  for reaching an agreement  with  Landlord and its
              agents as to the terms and  conditions  for all  contractor  items
              relating to the conducting of its work,  including but not limited
              to, those matters relating to hoisting,  systems interfacing,  use
              of  temporary  utilities,  storage  of  materials,   placement  of
              dumpsters,  access  to the  Premises  and  the  Building,  and the
              purchase and return of Building standard materials.

         (e)  Upon completion of any tenant improvements,  Tenant shall promptly
              furnish  Landlord with sworn owner's and  contractors'  statements
              and  full  and  final  waivers  of lien  covering  all  labor  and
              materials included in such  improvements.  Tenant shall not permit
              any mechanic's lien to be filed against the Building,  or any part
              thereof,  arising out of any improvement performed,  or alleged to
              have been performed,  by or on behalf of Tenant.  If any such lien
              is filed,  Tenant shall within ten (10) days  thereafter have such
              lien  released  of record or deliver  to  Landlord a bond in form,
              amount,   and  issued  by  a  surety   satisfactory  to  Landlord,
              indemnifying  Landlord against all costs and liabilities resulting
              from  such  lien  and the  foreclosure  or  attempted  foreclosure
              thereof.  If  Tenant  fails to have such  lien so  released  or to
              deliver such bond to Landlord, Landlord, without investigating the
              validity of such lien,  may pay or discharge the same;  and Tenant
              shall  reimburse  Landlord  upon  demand for the amount so paid by
              Landlord, including Landlord's expenses and attorney's fees.

     4. Landlord shall have the right to approve all  subcontractors  to be used
by the Tenant's contractor, which approval shall not be unreasonably withheld as
long as such subcontractors satisfy the requirements of this Article II.

     5.  Tenant  shall  indemnify  and  hold  harmless  Landlord,   its  agents,
contractors (including Building Contractor), and any mortgagee of Landlord, from
and against  any and all losses,  damages,  costs  (including  costs of suit and
attorneys' fees), liabilities, or causes of action for injury to or death of any
person,  for damage to any property,  and for mechanic's  materialmen's or other
liens or  claims  arising  out of or in  connection  with  the work  done by the
Tenant's    contractor   (and   Tenant's    contractor's    subcontractors   and
sub-subcontractors) under its contract with Tenant.

     6. The failure by Tenant,  after receiving  written  notice,  to materially
comply with any of the provisions of Article II of this Exhibit shall constitute
a Default  by Tenant  under the terms of the Lease and  Landlord  shall have the
benefit of all remedies  provided for in the Lease,  except  Tenant shall have a
thirty (30) day right to cure Default upon receipt of written notice .

     7. Upon  completion  of the Tenant  Improvements,  Tenant shall  deliver to
Landlord  two (2)  copies of the "as  built"  plans and  specifications  for the
Tenant  Improvements  completed  under Article II of this Exhibit  within thirty
(30) days of completing the same.

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