The marker offers a rare chance to be in four U.S. states at once, though there's some controversy over its geographic accuracy.

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

Paleoamericans built these ancient walls high in the Colorado Rockies as part of an extensive hunting system.

The remnants of a creative early method of wildfire prevention.

A nature and cultural preserve named for its multitude of petroglyphs carved by the Northern Sinagua people.

A mysterious spirit totem at the edge of Navajo lands.

The world's largest rose bush has literally outgrown the pioneer museum it was planted behind.

Some 2,000 carvings show this rare desert spring has been an oasis for travelers for over a thousand years.

This towering volcanic plug stands out among the dramatic formations that dot this otherworldly desert valley.

What was to be the world's most secure Cold War document vault ended up as just a few shallow caves.

This once bustling boomtown hotel is now the hottest spot in Nevada for ghost hunters.

The ruins of the "20-year town" lay out among the mountains of Alberta.

An ancient Viking village in North America that predates Columbus by 500 years.

An abandoned amusement park hints at the twisted history of the Newfoundland Railway.

In 1967, murder and mayhem disrupted the tranquility along this quiet stretch of Old Route 66.

A partial tunnel blasted into a steep ridge is all that remains of a failed railway across Arizona.

The old fire tower is one of the last of its kind in the United States.

The largest island on the great salt lake is home to curious creatures and strange stories.

River pirates, murderous bandits, and serial killers used this Illinois cave as their debauched hideout.

Home to the deepest rift anywhere on Earth.

Some of the tallest ancient American ruins continue to inspire awe and curiosity.

Once an ambitious nature spa, these forest ruins now provide a serene monument to failure.

Visit this playground of waterfalls, caves and sinkholes.

Sandstone rock formations that look like they belong on the cover of a progressive rock album.