Lakes Trasimeno and Bolsena, Italy
Sediments swirl in the Adriatic Sea off the east coast of Italy. Located near the center of the shoreline visible here is the port city of Ancona. Moving southwest across the Apennines, two lakes are visible: the green Lake Trasimeno and the dark blue Lake Bolsena.
Lake Trasimeno (or Trasimene) is the largest lake on the Italian peninsula south of the River Po, with a surface area of 128 km², slightly less than Lake Como. Trasimeno is surrounded for half of its shores by hills.
The Tiber River flows some thirty kilometers to the east of the lake, but the lake and the river are separated by hills: no major river flows directly into or out of Lake Trasimeno, and the water level fluctuates significantly according to rainfall levels and the seasonal demands from the towns, villages and farms near the shore.
Lake Bolsena, on the other hand, is a crater lake of volcanic origin, which was formed starting 370,000 years ago following the collapse of a caldera of the Vulsini volcanic complex into a deep aquifer. The lake is supplied entirely from the aquifer, rainfall and runoff, with one outlet at the southern end.
The lake has an oval shape typical of crater lakes. The long axis of the ellipse is aligned in a north-south direction. The bottom is roughly conical reaching a maximum depth at a point in the middle. The entire lake is surrounded by hills on the flanks and summits of which are the comuni. Elevations on the north of the lake are the highest, with a maximum of 702 m (2,300 ft).