India, May 17 -- From deep crimson canyons to cascading waterfalls, the world brims with natural wonders-and many can be found right here in the U.S. Some already top travel wish lists, like the beloved Grand Canyon. Others remain largely under wraps, like an American waterfall that produces one of the world's most consistent lunar rainbows.

Here are 12 of the most breathtaking natural wonders in the U.S., along with tips for the best time to visit.

01 of 12 Grand Canyon National Park, Arizona

Over six million years ago, the Colorado River began chiseling one of Earth's most lauded landscapes, the Grand Canyon. This 277-mile labyrinth of red crag in northern Arizona is like an ancient time capsule, with rocks on the canyon floor dating...