Which structure was the largest chariot racing stadium in ancient Rome?

The largest chariot racing stadium in ancient Rome was the Circus Maximus. This monumental structure was situated in the valley between the Palatine and Aventine hills and could accommodate a vast number of spectators, estimated to be around 150,000 to 250,000, making it one of the largest sports venues of the ancient world. The Circus Maximus was specifically designed for chariot races, which were immensely popular in Roman culture.

Unlike the Stadium of Domitian, which was a more specialized venue for athletic competitions similar to those held in Greek stadiums, the Circus Maximus was primarily used for chariot races and featured a long, oval track. The Augusta Treverorum, known today as Trier, was an important Roman city but did not have a stadium that matched the scale or function of the Circus Maximus. The Colosseum, while famous for gladiatorial games and various spectacles, was not primarily a racing venue and therefore does not fit the criteria of the question. The prominence and features of the Circus Maximus make it the correct answer for identifying the largest chariot racing stadium in ancient Rome.