The idyllic-looking Lake Sirino is situated in a karst sinkhole at the foot of Mount Sirino, and it was once part of the Pleistocene-era lake that occupied the entire length of the valley where the River Noce now flows.

The bed and shores of the prehistoric lake are made of Triassic limestone and Jurassic siliceous schists. The lake is fed by perennial springs, though in recent years, the water level has started lowering because of hydrological instabilities, like the opening of chasms that the water flows through and away from the lake.

The lake is surrounded by a street that has a small bridge crossing over a small meander of the water. A few commercial activities have sprung up around this natural attraction in the past few years. For instance, every summer a theatrical representation of some local legends and historical facts takes place on the lake.

One of these legends provides an alternative history of the lake's origin. According to this myth, before the lake there was a farmyard, but on a day devoted to the holy Madonna of Sirino, some farmers decided to work instead of dedicating the day to their families and praying. The sky became darker and darker until a strong storm broke out. The rain flooded the farmyard and killed the farmers and the animals. Even today, some say that when the wind is blowing between the mountains, the desperate howls of the oxen and the cries of the farmers can be heard.