The lake is surrounded by mountains; the Baikal Mountains on the north shore, the Barguzin Range on the northeastern shore, and the taiga are protected as a national park. It contains 27 islands; the largest, Olkhon, is long and is the third-largest lake-bound island in the world. The lake is fed by as many as 330 inflowing rivers. The main ones draining directly into Baikal are the Selenga, the Barguzin, the Upper Angara, the Turka, the Sarma, and the Snezhnaya. It is drained through a single outlet, the Angara.