Lake Kivu fills a corner of the Albertine Rift between DRC and Rwanda, and Goma sits on its northern shore. The water is unusually clear and largely free of the bilharzia and crocodiles that make swimming risky in many Central African lakes, so a lakeside beach bar at sunset, with a cold Primus and a plate of grilled tilapia, is one of the simpler pleasures of a visit to Goma.
The lake's other character is the geological one: enormous reservoirs of dissolved methane and carbon dioxide are held in its deep waters by the weight of the layers above. A large enough disturbance — a major earthquake or another lava flow — could in theory release a suffocating cloud of gas across the surrounding shoreline. The risk is low and actively monitored, and the lake remains beautiful, but it is part of the strangeness of Kivu that you cannot really separate the postcard view from the underlying volatility.