South Dakota's Badlands National Park is obviously the most famous example ... formations are found much further to the southwest in New Mexico's otherworldly Ah-Shi-Sle-Pah Wilderness.

Badlands National Park is a vast wilderness of jagged buttes, spires and pinnacles, mixed-grass prairies, and the world’s richest trove of fossils from the Oligocene epoch, estimated at 23 to 35 ...

New Mexico, home to Carlsbad Caverns National ... and national park sites nearby — like Custer State Park and Badlands National Park — that, in my opinion, are more impressive above ground.