Crater Lake is a caldera lake in the western United States, located in south central Oregon. It is the main feature of Crater Lake National Park and is famous for its deep blue color and water clarity. The lake partly fills a nearly 2,148 foot deep caldera that was formed around 7,700 years ago by the collapse of the volcano Mount Mazama. Today, there are no rivers flowing into or out of the Crater Lake.

Also, Crater Lake is known for the "Old Man of the Lake", a full sized tree which is now a stump that has been bobbing vertically in the lake for over a century. The low temperature of the water has slowed the decomposition of the wood, hence the longevity of the bobbing tree.

Currently, within the United States, Crater Lake is the deepest. In the world, it ranks tenth for maximum depth, and third for mean (average) depth.

More Info: en.wikipedia.org