The Campus Martius is an ancient square dedicated to Mars, covering an area of 25 hectares, located in Rome, Italy, outside the so-called Servian Wall. It is situated west of the Capitoline Hill at the bend of Tiber.
The original Campus Martius belonged to the last king of Rome, Lucius Tarquinius Superbus. After his exile, the king tried to negotiate a return of the square, but in reality he was aiming to regain his previous power. When the conspiracy came to light, deputies who were plotting together with the king were exiled from the city and their properties became the public domain.
Throughout the centuries, a lot of temples were built in the square: temples of Apollo, Bellona, Hercules and Muses, Juturna and Venus Victrix, the Circuc Flaminius as well as the national archives called Tabularium. By order of the Emperor, an artificial lake was created here, which was used as an arena for sea battles, naumachiae. The first one took place in 46 BC. The Campus Martius was incorporated into Urbs by the emperor Octavius Augustus.
In the beginning of the republican period in Rome, mayor civil events were organised in the Campus Martius, such as conscriptions, election meetings or qualifications, which took place every five years. In order to gather money needed for the war with Mithridates VI, a decree was issued in 88 BC, which conditioned a sale of the southern part of the square.
During times of the empire, the Campus Martius was converted from the centre of political life into a cultural place. Many representative buildings were erected, especially during the reign of Augustus, for example the Thermae of Agrippa, the Theatre of Marcellus and Balbus, the Pantheon, the Mausoleum of Augustus, the Portico of Octavia. Most of the successors of the Emperor added their own monuments, to commemorate their reign. Later, the Triumphal Arch of Tiberius was created there, and after that, the one of Neron emerged together with his amphitheatre and thermae. With the passing of years, the odeon was added, as well as the stadium of Domitian, the Triumphal Arch of Hanrian, the Temple of the Sun and the barracks of the municipal cohort of Aurelian.
In 271, the emperor Aurelian rebuilt the complex of walls, widening them and adding the Campus Martius into the city network.