Identify.

Circus Maximus, between Aventine and Palatine, 1st built by an Etruscan kings of Rome in 6th cent BCE, connected to Domitian's palace 81-96 CE, meta-turning points, could probably hold up to 15,000 people, usually used for horse games, could have also been used for religious processions, main obelisk now in Piazza del Popolo Spina