Lake Titicaca, lies at the highest level above the sea (12,507 feet) of any large lake in the world. It is in a basin surrounded by two ranges of the Andes Mountains. The lake forms part of the boundary between Bolivia and Peru. It is about 110 miles long and 35 miles wide at its widest part. Lake Titicaca covers an area of 3,261 square miles, more than one-third the area of Lake Ontario. A large part of the lake is more than 600 feet deep. The Desaguadero River flows out of its southern end and empties into Lake Poopo in Bolivia. Steamboats sail on Lake Titicaca.