A four-square-kilometre crater lake north of Taveta, Lake Chala has one shore in Kenya and the other in Tanzania. Very deep and remarkably blue, it is a bewitchingly beautiful landscape, completely unsuspected from the plains below. Chala is still paddled over by a few friendly fishermen in their dugouts and is spiritually significant, with lake monster stories part of local folklore. The lake is bilharzia-free and was also believed to be free of crocodiles. However, the death while swimming of a young British traveller in 2002, and the discovery of her body, missing an arm, points to the presence of crocodiles, and you are strongly advised not to swim here (though the Kenya sub-aqua club still runs regular diving trips here). While locals swear the crocodile responsible was killed a few years later, there’s no reason to think the reptiles won’t colonize the lake again. They are resourceful survivors, and have been known to trek overland for long distances.