Lake Chala, Volcanic crater lake at Kilimanjaro Region, Tanzania and Kenya.

Lake Chala is a volcanic crater lake straddling the Kenya-Tanzania border, rimmed by steep walls that rise dramatically from the water. The water shifts between turquoise, deep blue, and green depending on the season and light, surrounded by forests and open slopes.

Lake Chala formed about 250,000 years ago in a volcanic caldera east of Mount Kilimanjaro, on the Kenya-Tanzania border 8 km north of Taveta. Its surface sits below a crater rim up to 170 m high. Roughly 80 percent of the inflow is groundwater from Kilimanjaro's montane forest zone at 1,800 to 2,800 m, taking about three months to reach the lake.

The lake lies on the border, and its name appears in Swahili as Ziwa Chala and in German as Chala-See. Fishing boats work the water, and the Kenya Wildlife Service states that crocodiles live in the lake and swimming is not regarded as safe. In 2002 a Nile crocodile killed an 18-year-old British woman swimming at night.

The lake is accessible with hiking trails that circle the crater rim and offer views down to the water. Visitors can enjoy kayaking and birdwatching, with the driest and most comfortable conditions occurring from June through October.

The lake is home to the Chala tilapia, a fish species found nowhere else on Earth that faces serious danger of disappearing. This endemic species survives only in the specific conditions of this volcanic crater.