The Khari Khari Lakes are a pair of artificial reservoirs in the mountains southeast of Potosí, created in the 1570s as part of the vast hydraulic infrastructure that powered the colonial ore-processing industry. The Spanish engineers who designed the system — and the indigenous mitayos who built it — dammed mountain streams to create reservoirs that fed water wheels, which in turn drove the stamp mills crushing silver ore. At its peak, the system included 32 such lakes.
Today, the surviving lake at San Ildefonso is a scenic destination for walks and birdwatching, with the high Andean landscape providing an atmospheric setting. A trail of about 7 km leads from the city edge up to the lake through high-altitude scrubland. The walk is physically demanding above 4,000 metres, so go slowly and carry water. The setting gives a sense of the enormous investment the Spanish Crown made in extracting Potosí's silver — this was not artisanal mining but an industrial operation of extraordinary scale.