View of Trajan's Column through three archways

Originally, the site of the Roman Forum was a lake where waters from the surrounding hills drained. Because of its location, sediments from the erosion of the surrounding hills have been raising the level of the Forum floor for centuries. The low-lying wetland of the Forum was drained in the 7th century BC with the building of the Cloaca Maxima. Roman Forum developed gradually, over many centuries. Forum's long dimension extended from the foot of the Capitoline Hill to that of the Velian Hill. The Forum included a square, the buildings facing it, and, sometimes, an additional area (the Forum Adjectum) extending southeast as far as the Arch of Titus. The Forum functioned as an open-air market but eventually outgrew its marketplace role: political speeches, civil trials, and other public affairs dominated the Forum. An important function of the Forum was to serve as the culminating venue for the Triumphs. Victorious generals entered the city by the western Triumphal Gate (Porta Triumphalis) and circumnavigated the Palatine Hill (counterclockwise) before proceeding from the Velian Hill down the Via Sacra and into the Forum. In 600 BC Forum area was paved for the first time. The earliest basilicas (large, aisled halls) were introduced to the Forum in 184 BC by Marcus Porcius Cato, which began the process of "monumentalizing" the site. In the 80s BC, major work was done on the Forum including the raising of the plaza level by almost a meter and the laying of permanent marble paving stones. During early Imperial times, the economic and judicial business transferred away from the Forum. In the 5th Century AD Rome's population fell from 750,000 to 250,000. The populated areas contracted to leave Forum more or less intact. On 1 August 608, the Column of Phocas, a Roman monumental column, was erected. This proved to be the last monumental addition made to the Forum. By the 8th century, the Forum was surrounded by Christian churches taking the place of the abandoned temples falling apart at that time. During the Middle Ages, its location was called the "Campo Vaccino" or "cattle field." The structures of the Forum were dismantled and used to build towers and castles within the local area, the site became a dumping ground and a quarry for new buildings including the new Saint Peter's Basilica. The papal authorities eventually demolished many medieval structures on the site, to reveal and better display the ancient monuments. The Roman Forum has been a source of inspiration for artists for centuries.