Lake T'ana is the source of the Blue Nile and is the largest lake wholly in Ethiopia. It is approximately 52 miles (84 km) long by 41 miles (66 km) wide and is located in the country's north-west highlands (Lat 12° 0' North, Lon 37° 30' East). Greatest depth is 50 feet (15 m), over 1200 square miles (3000 sq km) in area at an elevation of 6,000 feet (1800 m). Islands in the lake have been inhabited for over 500 years by monks from Ethiopia's Orthodox Christian church. The remains of ancient Ethiopian emperors and treasures of the church are kept in the isolated island monasteries.