See massive fossils that are over 200 million years old in northeastern Arizona.

Ancient pueblos built into the base of a natural canyon wall.

A massive volcanic plug is now a protected area that hosts a number of bird species.

A grove of "candelabra redwoods" deep in California's Lost Coast.

This massive redwood tree has a hole in the base big enough to drive through.

On the Oregon coast is a natural hole that seems to be draining the sea.

A massive sea stack famous for its appearance in The Goonies.

This ancient cave is home to a museum, bar, and is filled with fluorescent minerals.

Giant, natural amphitheaters made of delicate geological formations called "hoodoos."

The hike through a narrow river flanked by the 2,000-foot-tall walls of Zion Canyon is one of the best in the world.

A tunnel with windows, so you don't miss out on the impressive views.

The unusual patterns in this rock formation result from two distinct modes of weathering.

The world's largest mountain carving could fit all of Mount Rushmore inside it many times over.

The first declared National Monument in the United States.

No Gordon Lightfoot song, only a barebones monument to greed.

One of nature's most well-scheduled phenomenons resides in Wyoming's Yellowstone National Park.

An architect's childhood fantasy treehouse made real.

A beautiful geyser under environmental threat.

This Yellowstone geyser may not shoot as high as the nearby Old Faithful, but it erupts for considerably longer.

The only natural lake in the world that drains into both the Atlantic and Pacific Oceans.

The largest hot spring in the United States is, as the name suggests, a stunning show of natural color.

The residents at this Yellowstone wildlife park will certify your cooler as "bear-proof."

A 6-mile-long lake created by an apocalyptic seismic event and the deadly chain reaction that ensued.

Around half a million years ago, these magnificent columnar basalt cliffs were formed from cooling lava.