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 fills a glaciated valley that is dammed in part by glacial till from the Pinedale Glaciation, and is younger than about 12,000 years. Natural tributaries to the lake are the North Inlet and East Inlet, 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.