Just under 2,000 feet deep, Crater Lake is the clearest, cleanest, and deepest lake in the country. To the Klamath Indians, it was a sight too sacred for human eyes, according to National Parks Traveler. They believe two spirits named Llao and Skell fought gruesome battles there. Llao ripped Skell’s heart, and Skell reacted by mutilating Llao and throwing his body parts into the lake, which still holds his spirit.