The remains of the ancient fortress Serdika are presented in the underpass between the Presidency and the Council of Ministers in Sofia City. The town of Serdika or Serdnopolis was founded 2,000 years BC by the Thracian tribe Serdi, who settled in the region around the hot mineral springs. In the 1st century AD the town was conquered by the Romans, who appreciated the important and strategic location and the mineral springs. During the reign of emperor Mark Ulpius Trayan (98 – 117), in his honor the town was called Ulpia Serdika and was turned into a center of the administrative area.