Lake Bolsena of central Italy, is a lake of volcanic and tectonic origin. Roman historic records indicate activity of the Vulsini volcano occurred as recently as 104 BC; it has been dormant since then. The two islands in the southern part of the lake were formed by underwater eruptions following the collapse that created the depression.
The lake is supplied entirely from the aquifer, rainfall and runoff, with one outlet at the southern end. A sewage treatment plant filters most of the raw sewage from the surrounding communities. Constructed in 1996, it features pipelines transporting the sewage from every major community around the lake to the treatment plant on the Marta River; that is, no effluents enter the lake. Fertilizers are a second source of contamination. However, the chemical content of the lake is monitored at several stations around it.
Address 01023, Italy
Coordinates 42°35'37.971" N 11°56'7.964" E