Phoenix: Tom's Thumb
Credit: David Tomlinson / Getty Images

Near Phoenix, Tom's Thumb Trail is a rewarding 4.5-mile hike that leads to the base of the granite monolith that gives it its name. From beneath the rock, hikers take in the sweeping view of Camelback Mountain – another hiking spot – and the other peaks surrounding the city. Serious hikers can extend the trip by veering onto a more rigorous loop.