An urban laboratory.

The artist James Turrell is repurposing an extinct volcano crater as an observatory to experience the cosmos.

A Saint Nicholas-themed ghost town in the Mojave desert.

America's only nuclear missile silo open to the public.

Ninety feet off the valley floor is an ancient dwelling put under protection of the U.S. government by Teddy Roosevelt.

A self-built castle made by a mysterious man.

A reproduction of earth's many biomes.

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

This secluded aqua waterfall in the Grand Canyon is the perfect swimming hole, and the Havasupai tribe's fiercely protected natural wonder.

The most powerful laboratory radiation source in the world pulses with 1,000 times the electricity of a lightning bolt.

One of the American Southwest's most extensive collections of Navajo rock art.

A half-acre utopia in the New Mexico desert features a graveyard, a game of horseshoes, a library, and a mailbox.

This innocuous New Mexico storefront was once the secret jump-off spot for Manhattan Project scientists.

An abandoned amusement park based on the popular 1940s Red Ryder comic strip.

These ruins of a pre-Columbian cliff village are among the most beautiful and well preserved in New Mexico.

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

These Pre-Columbian petroglyphs contain representations of birds, deer, hunters, and even some early Native flute players.

Air Force Academy Chapel made of 100 identical tetrahedrons works to inspire those of all religions.

This tea house was a hand-built gift from Boulder's sister city in Tajikstan.

These faux-cliff dwellings allow visitors to climb around on a replica archaeological site.

The childhood home of Henry Jones Jr. is now an adventure-themed bed and breakfast.

When ecosystems collide in the arid Southwest.

The largest self-built castle in the U.S., six decades in the making.

A breathtaking array of ancient Pueblo structures and artifacts counterintuitively preserved by neglect.