Rusting, graffiti-covered tanks litter the beach of this island, once used by the U.S. military for target practice.

The world's brightest bioluminescent bay.

The crumbling remnants of this 19th-century quarantine hospital hint at the touristy island's darker past.

Enormous lake at the bottom of a unique cave system.

A floating museum that was sunk by a flood and left to rot in the tides.

A flat slab of stone perched hundreds of feet above the Gasconade River in the northern Ozark mountains.

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.

For two weeks every June, fireflies in the Smoky Mountains perform an astonishing light show.

A hand-built folk art installation covered with messages of God's love.

An off-grid art installation that encourages its visitors to imagine a world without waste.

A hidden oasis just two minutes from downtown Atlanta.

An ornate Buddhist temple located in an Atlanta suburb, built by and for the Laotian community.

This hidden stone has absorbed decades of human anxiety.

The remains of an idyllic small town built for the film 'Big Fish' still stand around a rundown main street.

This ever-changing arrangement of naked dolls even caught the attention of "The Walking Dead" crew.

This folk art compound was built by a fortune teller on the advice of three people from the future.

On a barren hillside in the Yucca Valley, the recently restored Desert Christ Park has attracted pilgrims and kitsch hunters for over 50 years.

A fake town founded by Western movie stars is now becoming a hip desert community.

The "world's biggest dinosaur" once housed a creationist museum in its abdomen.

The ruins of a cotton mill that was burned in the Civil War are still hidden in a Georgia forest.

This large cave is a summer home to thousands of bats and has a rich history dating back to prehistoric times.

An abandoned railroad tunnel forgotten by time awaits inquisitive hikers.

The secret city built by the Manhattan Project.