Crater Lake National Park, the deepest, clearest lake in the United States, is truly breath-taking. Hours journeying through the surrounding national forests give no hint at what lies within the distant ridges. Then you climb. And climb. And all at once you step over a ridge top. Hundreds of feet below you lies 5 x 6 miles of the purest, bluest water you've likely ever seen. The lake was created around 8k years ago by the collapse of Mount Mazama volcano. Significant rain and snowfall in the area soon filled the crater, as did a small cinder cone volcano, Wizard Island, that erupted below the water's surface. As the lava cooled, the volcano quickly rose above the water, forming one of the two islands on the lake's surface. Apart from being one of America's greatest natural wonders, the lake is also considered by the Klamath Native Americans, who may have witnessed the lake's formation thousands of years ago, to possess great spiritual powers. Tribe members are still known to travel alone to the lake for days during vision quests.
Pro Tip: Visit the park during the week if you can. You can camp for free just outside the park in the surrounding National Forests. But make sure you get up for the sunrise. If you're lucky, you'll be the only one out there.