Lake Idro (also known as Lake Eridio) is 368 metres above sea level and the highest important lake in Lombardy. It is long and narrow and has a surface area of 11 sq km. It is flanked by steep mountains and in the north it opens on to a flat, fertile area of reclaimed land. Its tributary is the River Chiese. It is used as a reservoir by the electricity industry and for irrigating the Mantua, Cremona and Brescia plains. The most important towns on the lake are Anfo, on the left side, and Idro, at the southern end, both in the province of Brescia. Both have tourist marinas and little bathing beaches. State road no. 237 runs along the west side of the lake through the Rendena valley and Madonna di Compiglio. There is no ferry service on the lake.