28/06/2026
Lake Bolsena (Italian: Lago di Bolsena) is the largest volcanic lake in Europe and the fifth-largest in Italy, located in the province of Viterbo in northern Lazio. It sits at an elevation of 305 meters above sea level with a surface area of 113.5 km² and a maximum depth of 151 meters.
Geological Origin: The lake formed over 300,000 to 370,000 years ago when the Vulsinii volcanic complex collapsed after its magmatic chamber emptied, creating a large caldera that subsequently filled with water.
Hydrology: It is fed primarily by underground aquifers, rainfall, and runoff, with no major surface inflows. Its only outlet is the Marta River, which flows into the Tyrrhenian Sea near Tarquinia.
Key Features: The lake contains two islands, Isola Bisentina and Isola Martana, formed by underwater eruptions following the caldera collapse. It is renowned for its crystal-clear waters, which are among the cleanest in Europe, making it fully swimmable.
Tourism: Surrounded by medieval towns like Bolsena, Marta, Capodimonte, and Montefiascone, the area is a hub for sailing, windsurfing, and eco-tourism, easily accessible from Rome, Orvieto, and Viterbo.
