<PAGE>

                                                                EXHIBIT 10.13

                LEASE AMENDMENT NO. FOUR

Lease Amendment No. Four dated July 9, 1999 to be attached to and form a part
of that lease (which together with any amendments, modifications and
extensions thereof is hereinafter called the "Lease") made on the 30th day of
September, 1996 between SPIEKER PROPERTIES L.P., a California limited
partnership (successor in interest to BPG Pasadena, L.L.C., a Delaware
Limited Liability Company) as Landlord and TICKETMASTER ONLINE-CITYSEARCH,
INC., a Delaware corporation, (successor in interest to CitySearch, Inc., a
Delaware corporation) as Tenant, for the premises commonly known as 790 East
Colorado Boulevard, Pasadena, CA 91101 (the "Project").

The above described Lease shall be modified as follows:

RENTABLE AREA: Commencing September 1, 1999 through March 31, 2002, Tenant's
Rentable Area shall also include the entire fourth floor (approximately
13,666 rentable square feet) commonly designated as Suite 400 and that
portion of the fifth floor (approximately 1,999 rentable square feet)
commonly designated as Suite 508 of the Project. These Premises (totaling
approxmiately 15,665 rentable square feed) are more specifically outlined in
red on the attached Exhibits "A1" and "A2". Therefore from September 1, 1999
through March 31, 2002, Tenant's total Rentable Area shall be 46,321 rentable
square feet.

OCCUPANCY OF PREMISES: It is hereby agreed that, if the above described
fourth and fifth floor Premises become available to Tenant prior to September
1, 1999, this Lease Amendment No. Four shall commence one day thereafter. All
terms and conditions of this Lease Amendment No. Four, including that of
rental obligations, shall commence thereon. In the event the Premises are not
available until after September 1, 1999, Tenant shall have the right to
terminate this Lease Amendment No. Four. If Tenant elects to terminate this
Lease Amendment No. Four, Tenant shall provide Landlord with written notice
no later than one (1) day after Landlord notifies Tenant that the Premises
will not be available until after September 1, 1999. In the event Tenant
elects to occupy the premises after September 1, 1999, all the terms and
conditions of this Lease Amendment No. Four, including that of rental
obligations, shall commence one day after the Premises become available.

BASIC MONTHLY RENTAL: The Basic Monthly Rental shall be increased to reflect
the inclusion of these Premises. Therefore, the new rent schedule shall be as
follows:

<TABLE>
<CAPTION>

Period                                   Current             New                Total
------------------------------------------------------------------------------------------
<S>                                      <C>                 <C>                <C>
Commencement - October 31, 2000          $53,135.40          $30,080.00         $83,215.40
November 1, 1999 - November 30, 1999     $53,870.38          $30,080.00         $83,950.38
December 1, 1999 - August 31, 2000       $54,513.50          $30,080.00         $84,593.50
September 1, 2000 - September 30, 2000   $54,513.50          $31,645.00         $86,158.50
October 1, 2000 - August 31, 2001        $55,123.50          $31,645.00         $86,768.50
September 1, 2001 - March 31, 2002       $55,123.50          $32,740.00         $87,863.50

</TABLE>

TENANT'S PERCENTAGE SHARE OF OPERATING COSTS AND TAXES: The Premises
constitutes 12% of the total rentable area of the Building. As of the
commencement of this Lease Amendment No. Four, Tenant's percentage share of
operating costs and taxes shall be increased by 12% to a total of 35.47%.

BASE YEAR FOR OPERATING EXPENSES AND TAXES: Base Year for these additional
Premises (Suites 400 and 508) shall be calendar year 1999.

TENANT IMPROVEMENTS: Tenant accepts the Premises in its "as-is" condition.
However, subject to Tenant's presenting to Landlord paid invoices for
improvements performed to these Premises, Landlord shall pay Tenant the sum
of $62,660 on or within 30 days from September 30, 2001. All improvements
must be paid for by Tenant and approved by Landlord using Building Standard
materials and colors and in the Building Standard manner. As used herein,
"Building Standard" shall mean the standards for a particular item selected
from time to time by Landlord for the Building or such other standards as may
be mutually agreed upon between Landlord and Tenant in writing.


<PAGE>

PARKING: Tenant shall be allowed an additional forty-eight (48) unreserved
parking spaces at the Building's prevailing rate. As of the commencement of
this Lease Amendement, Tenant shall have a total of one hundred and
sixty-eight (168) unreserved parking spaces.

RESTORATION: Notwithstanding the terms set forth in Article 14 of the Lease,
provided Tenant installs Landlord approved tenant improvements and provided
the floor-plan is the same as Tenant's open floor plan on the second floor
and third floor of the Project, Tenant shall not be required to restore the
premises to the configuration upon which Tenant initially occupied the
Premises.

LEASE EXECUTION: In the event Landlord does not return a fully executed copy
of this Lease Amendment No. Four to tenant within three (3) business days
after Landlord's receipt of signed copies from Tenant, Tenant shall have the
right to terminate this Lease Amendment No. Four by notifying Landlord in
writing no later than four (4) business days after Landlord's receipt of
signed copies from Tenant.

CONTINGENCY: Tenant understands that these Premises are currently leased to
other tenants. At such, this Lease Amemdment No. Four is contingent upon
Landlord's successful termination of the existing leases on Suites 400, 508,
and 700.

All other terms and conditions of the Lease to remain the same.

IN WITNESS WHEREOF, the parties hereto have signed and sealed this Lease
Amendment No. Four as dated below.


LANDLORD:          SPIEKER PROPERTIES L.P.,
                   a California limited partnership
                   By:     Spieker Properties, Inc.,
                           a Maryland corporation
                   Its:    General Partner
                   By:  /s/ John Davenport
                      -------------------------------------
                            John Davenport
                            Regional Senior Vice President
                   Date:    7/14/99
                        -----------------------------------


TENANT:            TICKETMASTER ONLINE CITYSEARCH, INC.,
                   a Delaware corporation
                   By:  /s/ Tom McInerney
                      -------------------------------------
                            Tom McInerney
                            Chief Financial Officer
                   Date:    7/12/99
                        -----------------------------------