Arches National Park in Utah protects sandstone arches carved by wind and water. The arches are the signature attraction of the park, with many being easily accessible from the park road or hiking trails. Arches also preserves many arches in its out of the way back country.
Slot canyons are another unique feature of Arches National Park. Rangers guide hikes through the Fiery Furnace area of the park, explaining the geologic features. There are some tight squeezes on this hike.
Even a short visit can reveal much of the park, as the front country has a lot to offer in terms of short hikes to arches.
Arches National Park is close to Canyonlands National Park, which offers more backcountry to trek through than Arches.