The Uros are a pre-Incan people who live on forty-two self-fashioned floating islands in Lake Titicaca Puno, Peru and Bolivia.
The islets are made of totora reeds, which grow in the lake. The dense roots that the plants develop and interweave form a natural layer called Khili (about one to two meters thick) that support the islands. They are anchored with ropes attached to sticks driven into the bottom of the lake. The reeds at the bottoms of the islands rot away fairly quickly, so new reeds are added to the top constantly, about every three months. This is especially important in the rainy season when the reeds rot much faster. The islands last about thirty years.