The Uros Islands are a cluster of around 70 man-made floating islands in Lake Titicaca, about 30 minutes by boat from Puno. They are built from layers of totora reed that grows in the shallows; the bottom rots continuously, so islanders keep adding fresh layers on top. Stand on one and it shifts slightly underfoot.
The islands are the descendants of a community that moved onto the lake centuries before the Inca expansion. The original Uros language is no longer spoken — islanders today speak Quechua. Families split individual islands when relations break down, and islands can be moved by paddling or towing.
It is heavily visited and very commercial — vendors will approach you immediately. That said, the construction of the islands and the boats (shaped from bundled reeds into gondola-like forms) is genuinely interesting. The longer tours that continue to Taquile Island give a better sense of the wider lake.