The oldest building of this kind in Rome was the _Circus Maximus_, in the valley between the Palatine and Aventine hills, where, before the erection of any permanent structure, races appear to have been held beside the altar of the god Consus. The first building is assigned to Tarquin the younger, but for a long time little seems to have been done to complete its accommodation, since it is not till 329 B.C. that we hear of stalls being erected for the chariots and horses. It was not in fact till under the empire that the circus became a conspicuous public resort. Caesar enlarged it to some extent, and also made a canal 10 ft. broad between the lowest tier of seats (_podium_) and the course as a precaution for the spectators' safety when exhibitions of fighting with wild beasts, such as were afterwards confined to the amphitheatre, took place. When these exhibitions were removed, and the canal (_euripus_) was no longer necessary, Nero had it filled up. Augustus is said to have placed an obelisk on the _spina_ between the _metae_, and to have built a new _pulvinar_, or imperial box; but if this is taken in connexion with the fact that the circus had been partially destroyed by fire in 31 B.C., it may be supposed that besides this he had restored it altogether. Only the lower tiers of seats were of stone, the others being of wood, and this, from the liability to fire, may account for the frequent restorations to which the circus was subject; it would also explain the falling of the seats by which a crowd of people were killed in the time of Antoninus Pius. In the reign of Claudius, apparently after a fire, the _carceres_ of stone (tufa) were replaced by marble, and the _metae_ of wood by gilt bronze. Under Domitian, again, after a fire, the circus was rebuilt and the carceres increased to 12 instead of 8 as before. The work was finished by Trajan. See further for seating capacity, &c., ROME: _Archaeology_, § "Places of Amusement."
The circus was the only public spectacle at which men and women were not separated. The lower seats were reserved for persons of rank; there were also various state boxes, e.g. for the giver of the games and his friends (called _cubicula_ or _suggestus_). The principal object of attraction apart from the racing must have been the _spina_ or low wall which ran down the middle of the course, with its obelisks, images and ornamental shrines. On it also were seven figures of dolphins and seven oval objects, one of which was taken down at every round made in a race, so that spectators might see readily how the contest proceeded. The chariot race consisted of seven rounds of the course. The chariots started abreast, but in an oblique line, so that the outer chariot might be compensated for the wider circle it had to make at the other end. Such a race was called a _missus_, and as many as 24 of these would take place in a day. The competitors wore different colours, originally white and red (_albata_ and _russata_), to which green (_prasina_) and blue (_veneta_) were added. Domitian introduced two more colours, gold and purple (_purpureus et auratus pannus_), which probably fell into disuse after his death. To provide the horses and large staff of attendants it was necessary to apply to rich capitalists and owners of studs, and from this there grew up in time four select companies (_factiones_) of circus purveyors, which were identified with the four colours, and with which those who organized the races had to contract for the proper supply of horses and men. The drivers (_aurigae, agitatores_), who were mostly slaves, were sometimes held in high repute for their skill, although their calling was regarded with contempt. The horses most valued were those of Sicily, Spain and Cappadocia, and great care was taken in training them. Chariots with two horses (_bigae_) or four (_quadrigae_) were most common, but sometimes also they had three (_trigae_), and exceptionally more than four horses. Occasionally there was combined with the chariots a race of riders (_desultores_), each rider having two horses and leaping from one to the other during the race. At certain of the races the proceedings were opened by a _pompa_ or procession in which images of the gods and of the imperial family deified were conveyed in cars drawn by horses, mules or elephants, attended by the colleges of priests, and led by the presiding magistrate (in some cases by the emperor himself) seated in a chariot in the dress and with the insignia of a triumphator. The procession passed from the capitol along the forum, and on to the circus, where it was received by the people standing and clapping their hands. The presiding magistrate gave the signal for the races by throwing a white flag (_mappa_) on to the course.