Model of the ancient Campus Martius, seen near the lower left of the picture, around AD 300. When the Assembly of the Centuries used to vote on the Field of Mars in the Roman Old Republic, it had been an area outside the Pomerium, the exact boundaries of which have not been preserved. By this time, however, it was a perfectly rectangular field, surrounded by buildings very much inside the city proper.The Pantheon and the Fontana del Pantheon, a landmark of the Campus Martius since ancient Rome
The Campus Martius (Latin for 'Field of Mars'; Italian: Campo Marzio) was a publicly owned area of ancient Rome about 2 square kilometres (490 acres) in extent. In the Middle Ages, it was the most populous area of Rome. The IV rione of Rome, Campo Marzio, which covers a smaller section of the original area, bears the same name.
