It occupies a strip of coastal land from Anzio to Terracina, including also a sector of forest in the mainland of San Felice Circeo, and the island of Zannone.

It is characterized by the peculiar piscine ("swimming pools"), temporary marshy areas forming in the autumn season due to the accumulation of rainwater, and the lestre, where once the sparse population built their villages.

The berry vegetation allows the presence of a rich fauna, including wild boar, fallow deer, hare, european badger, red fox, weasel, green whip snake, Natrix maura, land and marsh Testudo, Triturus newt, toad and frog among the others.

The park is home to a 22 km-long coastal sand strip, from the limestone cliffs of the Mount Circeo, in correspondence of the Torre Paola watchtower, up to Capo Portiere.

The section nearer to the sea is home to short vegetation, housing a number of small size wildlife including the European badger, foxes, lizards and beetles.

Farther from the sea are bigger plants, such as the prickly juniper and mastic, up to true trees like the maritime pine and the holm oak, or, near the lakes (see following section), the alder, fraxinus, poplar and willow.