The best known examples of floating artificial islands are those of the Uros people of Lake Titicaca, who build their villages upon what are in effect huge rafts of bundled totora reeds. The Uros originally created their islands to prevent attacks by their more aggressive neighbours, the Incas and Collas. The larger islands house about ten families, while smaller ones, only about thirty meters wide, house only two or three.
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. This is especially important in the rainy season when the reeds rot much faster. The islands last about thirty years.