Grand Canyon National Park, AZ, USA: Deer Creek Falls. Hiking in is a different story. Trailhead access can be difficult, sometimes impossible, and the approach march is long, hot and dry, but for those making the journey the destination represent something close to canyon perfection. Deer Creek is a stop on most Colorado River Trips through the Grand Canyon.
Havasu Falls, Havasupai Reservation, Grand Canyon National Park, Arizona, United States. I hiked down to these falls (11 miles from parking lot), and it was every bit worth it! You need to plan on camping out a few days. It's too much to do in a short period of time.