The field of Mars in ancient Rome was an esplanade to the north of the Servian Wall, built by king Servi Tulli.
It was surrounded to the south by the Capitol Hill and to the east by the Pincià hill (Mons Pincius); the western limit was formed by the Tiber river. The name comes from the existence of an ancient sanctuary dedicated to Mars dating from the times of King Numa Pompili. A new temple on Mars was erected in 388 BC by the tribe Quint Cecili Metel Macedónico, to fulfill the promise made two years earlier during the invasion of the Gauls.