Crater Lake has inspired people for hundreds of years. No place else on earth combines a deep, pure lake, so blue in color; sheer surrounding cliffs, almost two thousand feet high; two picturesque islands; and a violent volcanic past. It is a place of immeasurable beauty, and an outstanding outdoor laboratory and classroom. Crater Lake is a caldera lake located in the south-central region of the U.S. state of Oregon. It is the main feature of Crater Lake National Park and famous for its deep blue color and water clarity. The lake partly fills a nearly 2,148-foot (655 m) deep caldera that was formed around 7,700 (± 150) years ago by the collapse of the volcano Mount Mazama. There are no rivers flowing into or out of the lake; the evaporation is compensated for by rain and snowfall at a rate such that the total amount of water is replaced every 250 years.