Lake Bolsena has a surface area of 114 sq km, is 14 km long and 12 km wide and is the largest volcanic lake in Italy. It covers a series of craters at the centre of the Monte Volsini volcanic group in the Viterbo area. It has a small catchment basin and a modest outlet in the River Marta who flows into the Tyrrhenian Sea. Its bottom is very irregular because of the islands of Bisentina and Martana which are probably fragments of the crater edge. It is well stocked with fish, especially eels. The lakeside towns of Bolsena and Montefiascone are linked by the Via Cassia road, while the smaller towns of Marta, Capodimonte and Valentano are linked by a system of good roads which allow you to drive right round the lake.