Known until the 19th century as the Circus of Caracalla it is part of a complex of buildings erected by emperor Maxentius around AD 306 and 312. The villa is situated between the second and third miles of the Via Appia near the basilica and catacombs of San Sebastiano and the imposing late republican tomb of Caecilia Metella, which dominates the hill that rises immediately to the east of the complex. The towers would have contained the mechanism for raising the carceres (starting gates), which were positioned on the course between the towers. Once out of the gates, the chariots would race down the track, the full 503 meters (550 yd) length of which can still be seen. The Circus itself is the best preserved in the area of Rome, and is second only in size to the Circus Maximus. The complex was probably never used after the death of Maxentius in AD 312.