Valmontone is a comune (municipality) in the Province of Rome in the Italian region Lazio, located about 45 kilometres (28 miles) southeast of Rome.
The historic part of the town is situated on a tuffaceous hill, 303 metres (994 ft) over the sea level, part of a morphological system of valleys and low relieves, known as Alta Valle del Sacco (High Valley of Sacco River). There are many natural springs due to the high water levels underground. Because of this the landscape is covered by forest and farmland.
To preserve this water system, in Valmontone exists the C.E.R.I., a center for the prevention and control of hydro-geological risks.
The origins of Valmontone are uncertain: it seems that a village was founded before the rise of Rome on a hill in the modern municipality of the town, and its ruins were visible until the 18th century. Perhaps these are the remains of the ancient Labicum, which, according to the myth, was founded by Glaucus, Minos’ son: the name of the village derives from a kind of Greek shield. Labicum was in war against Rome, but at last it was defeated and became a Roman castrum, a fortified castle: other testimonies of the Roman period are the post-station Ad Bivium, situated along the road called Via Latina, a village of coal-makers, some furnaces for tiles and vases, a villa and some other remains (two sarcophagus, memorial plates).