It is the latest, and by far the largest, of a series ofdata-center deals that have swept through Northern Virginia. Anaffiliate of Kimball Small Properties, Dataport is also building asuper-hub in San Jose and considering six sites in the New Yorkmetro area for a third.

Data centers are windowless, high-security, one-story flex orindustrial buildings. They house computers and telecommunicationsequipment that host Web services, house application-serviceproviders and route Internet and data telecommunications. Typicallyminded by a skeleton staff, they have been known to cost hundredsof dollars per square foot to equip, far more than even the mostrichly appointed office buildings. One center in Fairfax, VA costmore than $700 per sf.

Technology and telecommunications companies want to build datacenters in the area stretching roughly from Reston and Sterling toManassas because it is near Dulles International Airport, whichlinks to Washington via the Dulles Toll Road. America Online'sheadquarters is in Sterling and MCI/WorldCom's is underconstruction less than a mile away. Most important, all four majorproviders are laying the miles of fiber-optic cable needed to carryvoice, data and video transmissions. US Dataport's project would beclose to the new facility of Covad Communication and AmericaOnline's $500-million complex.