Rainbow Bridge is one of the largest arches accessible by foot or boat. It stands almost 300 feet wide and tall! Getting there by boat makes it a short and easy 1.3 mile hike to see the arch, and I love the 50 mile boat ride up the gorgeous Lake Powell.
Rockefeller Loop - Humboldt Redwoods SP, CA
The Rockefeller Loop is one of the best hikes you can do in Humboldt Redwoods - it's easy, short, and gives you everything you could want in a redwood hike - tall trees, an open under story, and both a river and a creek to relax by. The 7,000 acre Rockefeller Forest is also the world's largest contiguous old growth forest of coastal redwoods.
Blue Pools Canyon - Page, AZ
St. George Slot Canyon - Pioneer Park, St. George, UT
Backpacking Matlock Lake & Kearsarge Pass — Eastern Sierra Inyo NF, CA
Lower Antelope Canyon - Page, AZ
Horseshoe Bend — Page, AZ
Camping and Dune Boarding at Coral Pink Sand Dunes SP, UT
Coral Pink Sand Dunes is a small state park off the beaten path that is worth staying a night, or more if you have any dune toys like buggies, motor bikes, or ATVs. The campground had the nicest facilities of any park I've stayed at, and the pink dunes were impressive to see in the middle of the desert.