All along the coastline, from the Promontory's calcareous slopes to Capo Portiere, 25km up north, runs the characteristically crescent-shaped Coastal Dune of Circeo National Park.
The Park's coastal dune is a unique environment in Italy, and is therefore protected at European Union level, too.
The beach is made of fine sand and, behind it, the dune range can be as high as 27 metres.
High temperatures, long droughts, scarcely fertile land, and strong winds make it hard for plants to survive, and have forced them to develop specific ways of adapting themselves to this environment.
On the sea-facing slope, exposed to salty wind, halophyte plants grow, whereas the inland-facing slope, which is protected from sea winds, is characterised by Mediterranean scrub, home to a varied and timid fauna.
A road runs on the dune summit; by the Monaci Lake it is only possible to walk or cycle on it.
In the summer, thousands of tourists visit the coast to enjoy its wide beaches and wonderful sea, but the Dune shows its most spectacular side in the spring: luxuriant flowers turn it into a many-coloured mosaic, shining with sweet-smelling yellow Fabaceae and pink Silene. However, any time of the year is good to meet the interesting fauna living on the dune.
This sandy area, where many plants and animals constantly live at the mercy of wind, sea, and man, is a very fragile environment: not violating its spaces and keeping to the wooden boardwalks is the first rule to respect and preserve this spot of heaven on earth.