This palace on the northwestern side of the hippodrome was built in 416–418 and became imperial property after the downfall of its founder, the chamberlain Antiochos, in 421. In the following centuries, the palace gradually fell into ruins. Its hexagonal main hall was converted into a church of St. Euphemia in the late 7th century (not already in the 6th century as usually assumed) and survived as such until the end of the Byzantine Empire. The mausolea attached to it after the conversion are the latest known examples of this building type in Byzantium; in later times, narthexes and side chapels of churches were used for burials instead.