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

The world's longest known cave system.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

Where manatees are the snowbird vacationers in these balmy Florida springs.

Seemingly grown on some other world, these New Mexico rock formations look like a disused science fiction set.

An abandoned facility that has become a place of ritualistic satanic worship, or so rumor has it.

Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.

Olfactory delights in San Francisco's Botanical Gardens.

A prohibition-style speakeasy takes up residence in the last Victorian residence in Hollywood.

Towering basalt columns, a creation of fire and ice.

A house carved into a rock in the 1940s.

A beautiful geyser under environmental threat.

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.

The land is full of geologic eye candy, such as otherworldly spires, mushroom-shaped hoodoos, and prehistoric fossils.

Giant busts of 42 U.S. presidents are sitting in a field in Virginia.

The deepest lake in the United States, and once the site of epic destruction that lives on in legends.

Get lost in this haunting fairytale art walk through a man-made eucalyptus grove.

Here, at the "world's longest art gallery," you'll find forty miles of ancient petroglyphs and pictographs.

Hellam Township is reputed to feature seven remote gates, which when passed through in the right order, open an entrance to hell.

Explore the largest pure gypsum deposit in the world, and go dune sledding while you're at it.

The ancient dwellings of the Puebloans, located in the cliffs of majestic mesas.

This massive stained-glass masterpiece is thought to be the largest Tiffany dome in existence.

Under the right circumstances, this waterfall in Yosemite briefly turns a luminescent fiery orange.

Crystal clear lake with a shoreline of travertine located in a Colorado canyon.