The Ager Romanus (literally, the field of Rome') is the geographical rural area (part plains, part hilly) that surrounds the city of Rome. Politically and historically, it has represented the area of influence of Rome's municipal government. It is limited to the south by the Monti Prenestini range, Alban hills and Pontine Marshes; to the west by the Tyrrhenian Sea; to the north by the hills surrounding Lake Bracciano and to the east by the Monti Tiburtini range.