In the Roman Empire, chariots were not used for warfare, but for chariot racing, especially in circuses, or for triumphal processions, when they could be drawn by as many as ten horses or even by dogs, tigers, or ostriches. There were four divisions, or "factiones", of charioteers, distinguished by the colour of their costumes: the red, blue, green and white teams. The main centre of chariot racing was the Circus Maximus, situated in the valley between the Palatine and Aventine Hills in Rome. The track could hold 12 chariots, and the two sides of the track were separated by a raised median termed the "spina". Chariot races continued to enjoy great popularity in Byzantine times, in the Hippodrome of Constantinople, even after the Olympic Games had been disbanded, until their decline after the Nika riots in the 6th century. The starting gates were known as the Carceres.