It was once a lake that was drained in 1940. Today is merely a swamp which appears and disappears according to seasons, yetit has become an interesting zoological place where some rare amphibians survive (the northern crested newts, smooth newts, fire salamander, spectacled salamander) as well as interesting reptiles such as the grass snake which reproduces very well here.

From the adjoining Via del Vivaro (on the opposite side of the Marsh) a small path leads to the Bosco del Cerquone (Woods), where it is possible to admire some examples of centuries-old turkey oaks and English oaks, which are more than three metres diameter at breast height. We are talking about a unique botanic site inside the Castelli Romani area.