San Lorenzo Nuovo ("New Saint Lawrence"), which was moved from an older site (a hypothetical San Lorenzo Vecchio, "Old Saint Lawrence") further down the slope to avoid malaria. The northern shore of the lake once featured marshes, breeding grounds for the mosquitos that carry the disease. Currently it is agricultural. At the site of old San Lorenzo are Etruscan antiquities. To the north of San Lorenzo Nuovo and the caldera rim is Acquapendente. The hills to the east are to . Bolsena extends upward on the northeast shore, with Orvieto further to the northeast, at the edge of the volcanic region. On the southeast of the lake is Montefiascone at an elevation of , up on the ridge of Montefiascone caldera. To the south of the lake is Marta, on the right bank of the Marta River, sole effluent of the lake. The shore there is straight and developed. Elevations are within of the lake. Next to Marta are Valentano and Capodimonte, the latter being built on and around nearly the only headland on the lake, which forms a protective harbor. About to the south are Tuscania and Viterbo, the latter being the regional capital. From Valentano north is the Latera caldera, a shallow crater perhaps half the size of Lake Bolsena, with Lake Mezzano (usually too small for the map) at the western end. On its north rim is Latera. The floor of the caldera is mainly agricultural although the uncultivable rocky lava flows have been left forested. Although the hills on the west side of Lake Bolsena are only slightly higher than those on the south, the terrain is somewhat too rough for settlement. Fields extend as far as they can into v-shaped valleys and there is no flat shore. The hills to the north loom over the lake. At their western edge are Grotte di Castro and Gradoli. Geology Lake Bolsena is at the center of the Vulsinii (or Vulsino) Volcanic District of the Roman Comagmatic Region. The lake formed when a circular area collapsed after the depletion of the underlying magmatic chamber that fed the whole volcanic district. Although it is generally known as a volcanic lake, like its southern neighbor Lake Bracciano it is not a crater lake nor does it occupy a caldera. The major calderas of the area are found close to the lake's rim (Latera to the west and Montefiascone to the