Grand Lake is Colorado's largest and deepest natural lake. It is located in the headwaters of the Colorado River in Grand County, Colorado. On its north shore is located the historic and eponymous town of Grand Lake. The lake was formed during the Pinedale glaciation, which occurred from 30000 BP (before present) to 10000 BP. The glacial terminal moraine created a natural dam. Natural tributaries to the lake are the and , both of which flow out of Rocky Mountain National Park, which surrounds the lake on three sides. Grand Lake is located 1 mile from the Park's western entrance. Grand Lake was named Spirit Lake by the Ute Tribe because they believed the lake's cold waters to be the dwelling place of departed souls.