When ecosystems collide in the arid Southwest.

A clear blue swimming hole with hidden caves, still unexplored.

At this Denver landmark, the meals are compulsory, the sopapillas are complimentary, and the insanity is everywhere.

A museum dedicated to the alleged Roswell Incident.

Strange red rock formations that have been attributed to a higher power for hundreds of years.

Behind this beachfront shop lies a spectacular, colorful sea cave with an equally colorful past.

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

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

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

Home to items never before seen by the public.

A Pythagorean funhouse that tries, successfully, to prove that math is the coolest thing ever.

A semi-scholarly approach to sex.

Paranormal experiences in this hotel's room 217 led Stephen King to write "The Shining."

A house carved into a rock in the 1940s.

Try not to get slimed in Tribeca.

A treasure trove of artifacts, books, and artwork from the "golden age" of exploration.

An immersive environment that is part haunted house, part choose-your-own-adventure, and part jungle gym.

The granddaddy of all tourist traps, built on ice water, jackalopes, and a giant dinosaur.

Climbing this abandoned railway leads to breathtaking vistas of O‘ahu.

An authentic replica of an Asian temple and garden hidden amongst the natural beauty of Hawai'i.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

The Denver airport is guarded by a 32-foot-tall sculpture of a demonic horse.

Gaze upon chocolate sculptures depicting everything from chariot races to Gaudí's famous church at this shrine to sweets.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.