The Lagunas de Kari Kari are artificial lakes (ranging from an elevation of 4500m to 5025m) constructed in the late 16th and early 17th centuries by 20,000 indigenous slaves to provide water for Potosí and for hydropower to run the city’s 82 ingenios (smelters). Of the 32 original lakes only 25 remain and all have been abandoned – except by waterfowl, which appreciate the incongruous surface water in this otherwise stark region.
The easiest way to visit Lagunas de Kari Kari is with a Potosí tour agency, which charge about B$180 per person per day based on a group of three. If you prefer to strike out on your own, carry food, water and warm clothing. In a long day, you can have a good look around the lagunas and the fringes of the Cordillera de Kari Kari, but it may also be rewarding to camp overnight in the mountains (if you're fully kitted out with cold-weather gear).
Access is fairly easy, with public transportation from Potosí. Or negotiate with a taxi driver for the day; you can ask them to follow the road to Tupiza before making a left onto a rough, dirt road that leads up to the shore of Laguna San Sebastián. It's still best to inquire with one of the agencies in town and make sure you get a good map of the area. The Cordillera de Kari Kari is included on the IGM topo sheet Potosí (East), sheet 6435; nearby Cerro Kari Kari Central tops out at 5010m.