The Circus Maximus (Italian: Circo Massimo) was the first and largest chariot-racing course to be built in Rome. The Roman general, politician and future imperator, Gaius Julius Caesar, ordered its construction after a dream he experienced, wherein a huge racing arena that could host an entire population as an audience was built.
The Circus Maximus was first built solely for public entertainment and games by the Etruscan kings of Rome. After many years, Julius Caesar expanded the Circus to hold 270,000 to 300,000 spectators, because of the increased population of Rome. The track – able to hold 12 chariots – became 2,037 feet in length and 387 feet in breadth; each race set at the Circus went for a total distance of about 4 miles. 
In 140, one of the upper tiers of the circus collapsed and killed 1,112 spectators, an incident which remains the worst sports-related disaster in history. The last known chariot race was held by Totila in 549. Afterwards, the Circus was never used for large, public races, as most of the structure was destroyed by nature, and large sections of the track and seating disappeared. 
During the early Renaissance, the Circus was used by citizens for horse riding. Donato Mancini would participate in horse races there, and members of the Cento Occhi gang were also known to practice riding. Unfortunately for them, this habit resulted in them being tracked to the Circus and killed by Ezio Auditore da Firenze.