Circus, in ancient Rome, a place reserved for public games, races, and shows of different kinds. The circus maximus, in the valley now called Via de' Cerchi, was founded by Tarquin the Elder. It gradually became one of the most magnificent structures of Rome. The original temporary platforms erected at private expense, by patricians and equites, who alone witnessed the shows, were replaced by three galleries or tiers of seats, running in an elliptical form around the arena. Iron railings 12 to 14 ft. high, and a ditch 10 ft. broad and 10 ft. deep, a work of Caesar, separated the seats from and defended them against the furious beasts of the arena. Through its middle length ran a low wall called spina, at each end of which were erected three wooden (afterward gilt) cylinders of conical shape, forming the goals of races. The spina was adorned with gilt statues, images of deities, reliefs, altars, and chapels, and at its middle with an obelisk 132 ft. high, brought by Augustus from Egypt. There were also two platforms, on one of which reposed the images of seven dolphins, on the other the seven ova, imitations of eggs, which marked the numbers of the rounds done by the racers, one of the eggs being taken off after each.

At one of the narrow sides of the circus the galleries were wanting, and replaced by the stores for chariots and horses. The length of the circus was in the time of Julius Caesar more than 3 stadia, its breadth 400 ft., its circumference 8 stadia. Destroyed by fire under Nero, and rebuilt by Trajan, it was made by this emperor capable of containing 500,000 spectators, and completed under Constantine, who adorned it with another obelisk. The circus Flaminius or Apollinaris, erected probably by Caius Flaminius, in the Prata Flaminia, out of the city, and which in a show under Augustus was filled with water and became the scene where 36 crocodiles were killed; the circus of Sallustj near his gardens, destined for shows of sea fights; the Vaticanus, commenced by Caligula, completed by Nero; the Agona-lis, erected by Alexander Severus; those of Flora and Hadrian; and the circus maximus, were all destroyed. A circus attributed by antiquaries to Caracalla, near the Appian way, about two miles from the city, is the only one that remains in good preservation at Rome. More or less remarkable ruins of similar structures, erected in the ancient provinces of the Roman empire, are still visible in Alexandria, Rhodes, Athens, Gaza, Jerusalem, Nimes, Nar-bonne, etc. - In modern times the name is applied to a building or enclosure within which is contained a circular space designed for the exhibition of feats of horsemanship.

The most celebrated amphitheatre in London used for this purpose is Astley's. The present edifice is the fourth which has been erected upon the same spot, the three previous ones having been destroyed by fire. In Paris and Madrid there are several circuses, the finest of which in the latter city, the Circo de Price, is one of the largest and handsomest amphitheatres in Europe. In the United States equestrian performances are exhibited by companies which travel through the country during the summer months. The exhibitions are given in large tents. The wagons used for the transportation of these tents and the performers, with the exhibition horses, form a large train, and enter the towns and villages on their route in grand procession. The capital invested in each enterprise of this kind is very great, and the number of companies engaged in the business is considerable.