Old Latium was, in antiquity, the part of the Italian peninsula bounded to the north by the river Tiber, to the east by the central Apennine mountains, to the west by the sea and to the south by Monte Circeo. It covered an area measuring just 50 Roman miles. Mommsen calculated its area at ca. 1,860 square kilometres. It corresponded to the central part of the modern administrative region of Lazio (Italy) and was the traditional territory of the Italic tribe known as the Latins, to which the inhabitants of the archaic city of Rome themselves belonged. Later it was also settled by Rutulians, Volscians, Aequi, and Hernici. It was referred to as "old" (vetus) to distinguish it from the expanded region, denoted Latium by later Romans, that included the region to the south of Old Latium, between Monte Circeo and the river Garigliano - the so-called Latium adiectum ("attached Latium").