Crater Lake is situated in a 7,700-year-old caldera in the Cascades of south-central Oregon, United States. The focus of Crater Lake National Park, it is famous for its intense blue color and the clarity of its water. The lake is the deepest in the United States at 594 m (1,950 ft) and, though no rivers flow into or out of it, its waters are replaced every 250 years through rain and snowfall. A post-caldera cinder cone forms Wizard Island.Photograph: WolfmanSF