The second-largest ceremonial mound in the United States is an artificial hill that is loosely shaped like a pentagon.

A preserve with 75,000 ancient drawings remains the realm of public – not just scientific – exploration.

On the side of a remote mountain, a stone face bearing an inscription of mysterious origin.

One of the Eight Wonders of Kansas and the first official National Natural Monument these stark formations look like nature's Stonehenge.

This centuries-old pueblo church houses the body of a Franciscan friar who is said to be a rare "incorruptible" corpse.

Twenty-seven massive radio antennas on the high plains of New Mexico search for life on other planets.

A warm desert spring holds one of the rarest species on earth.

Wee (and not so wee) footprints that insects and reptiles of the Paleozoic Era left behind.

Despite time, colonization, and the brutal New Mexican heat, these Pueblo ruins still stand.

One believer transformed a local curiosity into proof of Vikings on the Great Plains.

Natural catch-basin rocks covered in thousands of drawings spanning many millennia.

A cave's rare beauty held a cavernous secret hidden underground.

Steep canyon walls hide a forested oasis in the West Texas desert.

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

The highest point in Texas is capped by a big silver pyramid.

The legend of a local monster still haunts this small town.

Mysterious glowing orbs float through the desert night.

Inside this mountain lies several kilometers of breathtaking caves.

In Paris, Texas they have their own Eiffel Tower, it just has a cowboy hat on it.

This small town Texas cemetery is said to be the burial site of a UFO pilot who crashed in the 1800s.

Scale replica of China's ancient terracotta tomb warriors and Forbidden City are the side project of an eccentric millionaire.

This sacred cavern, 400 feet deep, is home to millions of bats and an ancient burial ground.

An enormous pink granite batholith, long attributed with spiritual powers by the Tonkawa Indians.

Beneath Kraków Old Town's main square lies a hologram-filled medieval market vampire graveyard wonderland.