Barcelona's historic 19th-century sewers, whose foundations were laid in medieval times, are open to the public for exploring.

Mountain where Jesus was first tempted by the Devil.

This lovely university observatory continues to sit abandoned since its potential savior was sent to jail for fraud.

The tragic reality of a town riddled with rumors of haunts, chemical spills, and serial killers.

The overgrown remains of an old rail bridge rise above the valley like ancient Greek ruins.

There is beauty and history in the ruins of this former company town.

This abandoned bridge to nowhere stands secluded in the woods of a Cleveland suburb.

The only Florida state park with publicly accessible caves.

An abandoned water sports stadium that has become a haven for graffiti and decay.

An abandoned vacation home spent a decade taking on legends. It's now taking on water.

A luxurious 1880s hotel with its fair share of Tiffany stained glass, Edison electricity, and of course, ghosts.

Where manatees are the snowbird vacationers in these balmy Florida springs.

The scuba diving training facility was named for the steam that rises from the cave's chimney.

This spectacular public market has got meat, fish, vegetables, baked goods, and enough kielbasa for a lifetime.

Deep scars on the earth left by the Ice Age.

The inventor of a number of hybrid corn species is immortalized with a field of giant corn.

These sub-farmland caves are home to a majestic stalactite known as the "Crystal King."

Rare recess caves fill this unbelievably beautiful Ohio park.

An abandoned relic of the city's failed experiment with below ground transit.

The angel of death appears to weep black tears at this grave marker.

Formerly secret, precariously perched boulders.

Despite a legend that says this highest peak in Oregon was climbed in high heels scores of people have died on its slopes.

Not-so-fearsome tiny trolls live under this wooden train trestle in Portland.

The eerie remnants of an ancient forest were hidden under the sand for centuries.