Top 10 Things You Didn't Know About National Parks

Deep Blue
Southern Oregon is home to the deepest lake in the U.S., in Crater Lake National Park. Lying in a volcanic basin, Crater Lake was created when the 12,000-ft.-high Mount Mazama collapsed 7,700 years ago following a large eruption. It is 1,943 ft. deep — deep enough to hide 1½ Empire State Buildings. About 530 in. of winter snow per year provide the lake with plenty of water and ensure that these still waters always run deep.

• Ken Burns, American Filmmaker