The world's largest man-made underground caverns offer unparalleled underwater wonders.

This abandoned prison castle has become an imposing gallery of graffiti art.

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

Less a museum than a bizarre fantasy world created by artists and engineers.

European castle ruins in an American state park are actually the product of death and grief.

This museum houses artifacts from American adventurers and filmmakers Martin and Osa Johnson.

Tribute to the famous Notre Dame football coach who died in a plane crash.

This statue is an ode to an iconic roadside advertisement popularized during the 1970s.

Journey up the capitol building's cupola for an amazing view of Topeka.

Step back in time at this 1950s display home, built to showcase once cutting-edge electric amenities.

Self-built house and sculpture park where the creator can still be seen in a glass coffin.

These elevated trucks were put in place as a middle finger to The Man, but are now considered folk art.

A unique attraction and museum dedicated to exploring iconic roadside structures.

A technicolor place of worship for Elevationists.

This modern antique shop is a museum for 1980's Saturday morning cartoon culture.

This grand stone tower was dedicated to a famed American humorist almost by coincidence.

The haunted reputation of these abandoned Colorado train tunnels is probably not helped by the terrifying spiked fence.

Thanks to a quirk of elevation this gift shop produces magic doughnuts that are found nowhere else on Earth.

A prehistoric rock shelter that's literally in someone's backyard.

This super steep hike ascends 2,000 feet in less than a mile.

High atop a Mexican rainforest mountain, this ancient pyramid once drew pilgrims countries away.

Extraordinary sculpture garden created by an eccentric English poet.

A gargantuan crystal kingdom.

These azure waters were thought to lead to the Mayan Underworld.