Yellowstone National Park
Yellowstone National Park has one of the world's largest petrified forests, trees which were long ago buried by ash and soil and transformed from wood to mineral materials. This ash and other volcanic debris are believed to have come from the park area itself as the central part of Yellowstone is the massive caldera of a supervolcano. The park contains 290 waterfalls of at least , the highest being the Lower Falls of the Yellowstone River at .
Cuyahoga Valley National Park
The natural areas include forests, rolling hills, narrow ravines, wetlands, rivers, and waterfalls. About 100 waterfalls are located in the Cuyahoga Valley, with the most popular being the tall Brandywine Falls—the tallest waterfall in the park and the tallest in Northeast Ohio. The Ledges are a rock outcropping that provides a westward view across the valley's wooded areas. Talus caves are located among the boulders in the forest around the Ledges.