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Clues:
 * This immense gorge can be a mile deep and up to 18 miles wide.
 * The location boasts some of the nation's cleanest air, with visibility on clear days averaging 90 to 110 miles.
 * This canyon was formed due to erosion from the Colorado River

Questions to answer: 1. What is the name of the National Park? 2. How long in miles is this canyon?

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