It is a majestic building with a quadrangular plan and an internal courtyard, located in the south-east corner of the ancient Roman forum, between Piazza delle Erbe and Piazza dei Signori. A "domus communis" built in the 12th century to house the new municipal magistrates, incorporating various pre-existing buildings, as was typical in the early medieval period, it was originally defended by four mighty corner towers, of which today only those facing Piazza delle Erbe remain. Among these is the famous TORRE DEI LAMBERTI, built in 1172 and raised several times until it became the tallest tower in the city.