Albeni Falls Dam sits on the Pend Oreille River. Behind the dam, the waters of the Pend Oreille stretch 65 miles through a glacially carved valley that separates three mountain ranges. Rimmed by mountains that rise 6,500 feet, Lake Pend Oreille is one of the largest and deepest natural lakes in the western United States. In some areas, it plunges to a depth of 1,237 feet.