The first circus used for chariot races lying in the valley between the Aventine and Palatine hills is said to have been built by king Tarquinius Priscus even if there are testimonies of similar races held at the time of Romulus. The track was originally bordered by banks of wooden seats. Later the starting stalls (carceres), the spina, which divided the racecourse, and stone seats were added to the older structure.
In 10 b.C. Augustus brought from Heliopolis the obelisk of Rameses II 24 mt high ( which today graces the Piazza del Popolo), to occupy the centre of the circus and in 357 A.D. also the obelisk of Thutmosis III 32mt high was added (by wish of Pope Sixtus V it stands today in the Piazza S.Giovanni in Laterano).
The circus was enlarged by Caesar and Augustus added to it the pulvinar (royal enclosure or sacred area).Its seating capacity was of around 150,000 people till the reconstruction by Nero who, after the great fire of 64, increased the number of seats to 250,000. Further enlarged it reached the colossal dimension of 600 by 200 metres. Today few remains are still preserved at the southeast end. In 1931 by the northwest end a brickstone edifice dating back to the Imperial Age ( probably a tribunal) was discovered, it was transformed in the III cent. A.D. in a Mitreum (today under the basement of the ex- pasta factory Pantanella).