Rivalling the attraction of the Blue Nile Falls are the thirty-seven islands scattered about on the 3,000-square-kilometre (1,860-square-mile) surface of Ethiopia’s largest body of water: Lake Tana, which gives birth to the Blue Nile. Some twenty of these shelter churches and monasteries of immense historical and cultural interest; decorated with beautiful paintings and housing innumerable treasures. Lake Tana, largest lake of Ethiopia, located in a depression of the northwest plateau, 6,000 feet (1,800 metres) above sea level. It forms the main reservoir for the Blue Nile (Abbay) River, which drains its southern extremity near Bahir Dar. The lake’s surface covers 1,418 square miles (3,673 square km), with a surrounding drainage of 4,500 square miles (11,650 square km); its maximum depth is 45 feet (14 metres). The islands and peninsulas of Lake Tana are most conveniently approached by boat from Bahir Dar on the southern side of the lake, though boats can often also be obtained at Gorgora on the northern shore. The many interesting and historic locations on or around the lake include the islands of Birgida Maryam, Dega Estefanos, Dek, Narga, Tana Cherkos, Mitsele Fasilidas, Kebran, and Debre Maryam, as well as the Gorgora, Mandaba, and Zeghe peninsulas. All have fine churches. Though founded much earlier, most of the actual buildings date from the late sixteenth or early seventeenth centuries. Many have beautiful mural paintings and church crosses, and house crowns and clothes of former kings.