5. Trip to the Grand Canyon
The best way to avoid crowds is to come at the right time of the year. The busiest time of the year is from Memorial Day (late May) to Labor Day (early September), which is also the hottest time of the year. December before Christmas, January and February are the slowest times of the year.
The view from the southern edge is spectacular for the vast panoramas, but to experience the canyon. You should take the time to do at least a short walk below the rim and see it on a different scale. If geology has always seemed boring to you, the Grand Canyon is the place to prove you wrong.