The forum was the centre of political, commercial and judicial life in ancient Rome. The largest buildings were the basilicas, where legal cases were heard. According to the playwright Plautus, the area teemed whit "lawyers and litigants, bankers and brokers, shopkeepers and strumpets, good-for- nothings waiting for a tip from the rich".
As Rome's population boomed, the forum became too small. In 46 BC Julius Caesar built a new one, setting a precedent that was followed by emperors from Augustus to Trajan. As well as the Imperial Forum, emperos also erected triumphal arches to themselves, and just to the east Vespasian built the Colosseum, centre of entertainment after the business of the day.
The formation of the Forum valley was to the erosion of a bank of volcanic tufa by a stream named the Velabrum, which meandered between the Palatine and Capitoline hills toward the Tiber.
Used ad a necropolis in the Iron Age (10th to 9th century BC), this marshy area was drained at the beginning of the rule of the Etruscan kings, when Tarquinius Priscus is said to have channeled the waters of the Velabrum in order to implement a series of public works, the most important being the city's huge sewer, the cloaca maxima.
Rome then began to developer on this site, which remained its political, administrative and religious center until the end of the Republican period.
During the Middle Ages, when the population gradually settled in the Campus Martius, the Forum although strew with debris came to be used as grazing for cattle and acquired the name of Campo Vaccino ("the cattle field"). It was not until the 19th century that the archaeologists began to unearth the half-buried ruins, digging sometimes as deep as 65 feet.