The lake forms naturally at the west end of the basin in a depression constantly filling with spring water exuding from the base of the mountains, which are a heavily cracked and faulted limestone karst absorbent of most rainfall.

All the coastal lagoons of Lazio formed in the same way: an offshore Pliocene graben created by extensional forces in NE and SW directions behind a karst of Mesozoic limestone gradually filled by peaty and fluvial deposition in the Pleistocene.

A barrier fringe of sand developed offshore enclosing first a lagoon, then a coastal marsh.

In the last few centuries bonifica or "restoration", of the marshland to produce agricultural land, and associated control of the water channels, have stabilized the lakes as landforms.

In 2008 a group of scientists from the University of Salento published a study of biodiversity in 26 Italian lagoons.