Lake Lanao is a vast tectonic lake — about 340 square kilometres, 700 metres above sea level — that defines the geography of Marawi and the surrounding province of Lanao del Sur. The Maranao people ("people of the lake") have lived around its shores for centuries, and the lakeshore is dotted with stilt houses, mosques, and small markets.
The lake's water level dropped significantly after the Agus hydroelectric system was built in the 1950s, and the endemic fish that gave the lake its scientific importance are now mostly gone. The view is still extraordinary — particularly at sunrise from the northern shore — and the boat traffic of long, brightly painted Maranao vintas gives a sense of how the town has functioned for centuries.