This 4,000-foot-diameter hole is touted as "the most well known, best preserved meteorite crater on Earth."

A stealthy Apache hideaway that became the haunting site of a mass grave.

The story of Two Guns, Arizona could easily be described as a Shakespearian tragedy on Route 66.

The final resting place of the businessman-turned-astronomer who helped discover Pluto stands near his observatory.

This Arizona observatory is famous for investigations into Martian life, and as the place humans first spotted Pluto.

A planet-hunting astrograph built in the 1920s to seek out the so-called "Planet X" beyond Uranus.

An important piece of history from mankind's journey to the moon sits in the lobby of a government science lab.

One of the most extensive and well-preserved collections of dinosaur footprints in North America.

A sharp bend in a dramatic river canyon cut through red rocks.

Most-visited and most-photographed slot canyon in the American Southwest.

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

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

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

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

Bizarre lunar-like landscape with thousands of large stone "hoodoos."

The fifth-longest natural arch in the world, and the longest outside China.

This interpretive path lets you get up close and personal with dinosaur bones.

Inside this striking glass building, visitors can see thousands of dinosaur fossils in the positions that nature deposited them more than 150 million years ago.

One of the largest collections of wildlife art in the United States, built into the side of a cliff in rural Wyoming.

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.

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

One man's ambition created this psychedelic log home.