This once-popular otherworldly landscape was formed by one of the largest volcanic eruptions in history.

When ecosystems collide in the arid Southwest.

This Colorado hiking trail provides a small gold mine of abandoned gold mines.

This enigmatic building features numerous architectural styles.

The moving metal works of one troubled artist can still be viewed on his front lawn... for now.

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

This Boeing KC-97 tanker is now a restaurant for aviation lovers.

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

The superstar of Cold War nuclear bunkers has been featured in countless films but is now barely operational.

Hidden beneath a bridge, this waterfall is known for the large amounts of graffiti painted on its base.

Visitors to this arboretum are greeted by three smiling giants crafted from sustainable materials.

A local scoured more than 1,000 acres for stone to create his masterpiece.

A natural sandstone bridge hidden in the Sewanee forest.

This former maximum-security prison is creepy, sobering, and supposedly haunted.

This funicular railway rumbles along for a mile up the nearly vertical face of Chattanooga’s Lookout Mountain.

Visit this playground of waterfalls, caves and sinkholes.

Eight rare Corvettes are swallowed up by a sinkhole in Kentucky's National Corvette Museum.

One man’s religious convictions led him to build this stone castle meant to withstand an apocalypse.

An ancient cave system in Tennessee’s Appalachian foothills converted to a 1,200-person music venue.

One man has spent decades faithfully constructing this unique brick and cinderblock castle.

A reclusive Memphis neighborhood is home to decades worth of misunderstood Masonic folk art.

The hotel where Martin Luther King Jr. was shot is now a museum dedicated to his work.

This head-spinningly bizarre Depression-era art cave is wall-to-wall quartz and Jesus.

Wild lights and sound effects turn a walk through some caves into an eye-popping 1960s tourist attraction.