The Fontaine d’Eau Chaude was the first fountain built on the Cours Mirabeau — in the 1600s. The hot water (34°C/64°F) comes from the hot springs of Bagniers. There are current photos here and here, showing it still covered in moss.
If you would like to see and read more about living in Rwanda, check out the charming blog A Year+ in Kigali, Rwanda by Helaina. I particularly liked her posts here (about the language) and here (culture) and here (food).
Her photo of this female mountain gorilla is one of the best that I have seen. (And, living here, I’ve seen quite a few.)
Also, here’s something I just found out: the smallest waterlily in the world, Nymphaea thermarum, was native to the hot springs of Mushyuza in southwest Rwanda. Unfortunately, it has not existed in the wild since 2008, when its habitat was disrupted by farming. However, in 2010, a scientist at Kew Royal Botanic Gardens was finally able to germinate its seeds (there were only 20 left). Its flowers, which are only about 1/4″ (less than 1 cm.) in diameter, are white/lavender with yellow stamens.