Few people know Lake Chala.
Located half in Kenya and the other half in Tanzania, under Kilimanjaro, between the towns of Taveta and Loitokitok, Chala is a crater four square kilometers in diameter surrounded by greenery.
Very deep and extraordinarily blue, it presents a landscape of bewitching beauty, completely unsuspected by the plains below.
The Chala is frequented only by a few friendly fishermen in their shelters and is spiritually significant, with stories of lake monsters that are part of local folklore.
From the edge of the 100m high crater, there is a steep descent to the lake and good hiking shoes are recommended.
You can spot lizards of various species, baboons and monkeys and, if you are lucky, dik-dik and bushbaby.
A great place for birdwatching, the bird list has more than 250 species, including peregrine falcons, which nest in the Chala cliffs.
The lake is filled and drained by underground watercourses fed by water flowing off Kilimanjaro.
There are some lodges on the Kenyan side of the lake, which are about 30 minutes walk from the lake and have affordable prices (25-30 euros per night). 
From there it is a nice walk to the lake, where someone dares to take an unforgettable swim.
It was also once believed to be free of crocodiles.
However, a crocodile killed a young British traveler who was swimming here in 2002, and it is still highly recommended not to enter the water, despite the locals swear that the responsible crocodile was killed a few years later and that there is no reason to think that other dangerous reptiles still frequent the lake.
Surely the virgin landscape, among the many places to visit in Kenya, is worth discovering.