The Roman circus was a race-track.
None has survived intact but enough of the one in Mérida, Spain, is left to give you the feeling of the place. It was built at the time of Christ.
Remains of the Roman Circus at Merida, Spain (Creative Commons Attribution-Share Alike 3.0 Unported license photo by Andrew Kingsolver)
It was one of the most important race-tracks in the Empire—big enough for thirty thousand spectators. The track itself was enormous—thirty thousand square meters (three soccer fields).
In the center, dividing the track in two, was a long narrow island called the spina, full of rich decoration such as obelisks and statues of all kinds. At the head of the track were carceres—the little rooms where the chariots waited before taking positions at the starting gate.
The Romans loved these horse-races even better than the gladiator combats in the amphitheaters. The best charioteer of all times was probably Gaius Apuleius Diocles, a Portuguese (Lusitanian). He triumphed in Rome but he no doubt got his start at the Mérida track.
.a scene from the movie Ben Hur (fair use sceenshot)
No one knows exactly when the last race took place in the Mérida circus. Chariot racing declined when Christianity was made the official religion of the empire. The Councils of Elvira and Arles expressly prohibited the profession of chariot driver (and clowns). Yet there is an inscription in one of the carceres that declares that in 340 the circus was renovated. And there is a sixth-century tombstone in a Mérida graveyard to honor a famous chariot driver called Sabiniano.