The Campus Martius, or Field of Mars, was a publicly owned area of ancient Rome about 2 km² (600 acres) in extent. It was dedicated to Mars, the Roman god of war, and was used for pasturing horses and sheep, when it was not a focus of military training activity. Since it was outside the walls of Rome until the Aurelian wall was built, the Campus Martius was a natural place for audience given to foreign ambassadors who could not enter the city, and foreign cults were housed in temples erected there.

The Campus Martius itself was a low-lying plain west of the via Lata, the modern Corso next to a bend in the River Tiber. According to one legend, it was once a field of wheat owned by Tarquin, last King of Rome, but was burnt during the revolution which established the Roman Republic. Dedicated to the god of warfare with an ancient altar, the Campus Martius was closely linked to soldiers and the army. Initially, the field was often used by soldiers for purposes of training. Later, it was frequently the focus of Triumphs, the celebrations of a successful military campaigns.

Starting in the time of Sulla, building lots were sold or granted to influential romans, and insulae (apartment blocks) and villas encroached on the common land. It later became a point of assembly for civic meetings, and of the city's militia. Pompey built the first stone theater in Rome in the Campus Martius in 55 BC Agrippa had the swampy ground made into a pool and baths in a setting of parkland and temples, and built the Porticus Argonautarum and the Laconicum Sudatorium . In 33 BC Octavian dedicated there the Porticus Octavia, built from spoils of the Dalmatian War .

The Campus Martius also held the Ara Pacis (Altar of Peace), built by the Senate to mark the establishment of peace by Augustus. It was intended to symbolise the successful completion of Augustus's efforts to stabilize the Empire.

Gradually, as the city of Rome expanded at the end of the Republic and in the early Empire, more and more buildings were constructed on the Campus Martius. Prominent new structures included the Mausoleum of Augustus , the Theatre of Marcellus . The Campus filled with temples and public buildings, circuses, theaters, porticoes, baths, monuments, columns and obelisks.

After the barbarian invasions cut the aqueducts, the rapidly dwindling population abandoned the surrounding hills and concentrated in the Campus Martius, depending on the Tiber for water and victimized by its flooding. The Campus Martius contained the main part of Rome until the new developments increased the size of the capital of a reunited Italy after 1870.

External link

• Detailed topographical history of the Campus Martius