Rila has abundant water resources. Some of the Balkans' longest and deepest rivers originate from Rila, including the Maritsa, Iskar and Mesta rivers. Bulgaria's main water divide separating the Black Sea and the Aegean Sea drainage systems follows the main ridge of Rila. The mountain range is dotted with almost 200 glacial lakes such as the renowned Seven Rila Lakes, and is rich in hot springs in the fault areas at the foothills, including the hottest spring in South-eastern Europe in Sapareva Banya.