The walls enclosed all the seven hills of Rome plus the Campus Martius and, on the right bank of the Tiber, the Trastevere district. The river banks within the city limits appear to have been left unfortified, although they were fortified along the Campus Martius. The size of the entire enclosed area is . The wall cut through populated areas: in reality the city at the time embraced 2,400 hectares or 6,000 acres. Pliny the Elder in the first century A.D. suggested that the densely populated areas, 'extrema tectorum' (the limits of the roofed areas) extended from the Golden Milestone in the Forum (Natural History 3.67).