the capital city of Bulgaria. ancient Serdica City (pop., 2001: 1,096,389), capital of Bulgaria. Established as a Thracian settlement 8th century BC, it flourished under the Romans. Plundered by the Huns in the 5th century AD, it was rebuilt under the Byzantine Empire. In 809 it became a Bulgarian town but reverted to Byzantine rule from 1018 to 1185, when the second Bulgarian empire was established. The Turks held it from 1382 until it was liberated by the Russians in 1878. In 1879 it was made the Bulgarian capital. It is the country's principal transportation and cultural centre and the site of many industries. Among its educational institutions is the University of Sofia (1888), Bulgaria's oldest university. Its historical monuments include the 6th-century church of St. Sofia
Stratospheric Observatory for Infra-red Astronomy A strospheric aircraft (Boeing 747HP) carrying a 2 5 meter telescope for observations at optical to submillimeter wavelengths Successor to the Kuiper Airborne Observatory First test flights expected late 2004 For more information, see http: //sofia arc nasa gov