This stunning gothic ruin was a casualty of the Indiana steel industry crash.

This railroad track was so secretive that it was omitted from all maps.

Built to transport German U-boats through the never-completed Masurian Canal, the locks near this Polish village are now home to a rope course.

An ancient and majestic fortress that played an integral role in Portugal's road to independence.

The verdant mossy ruins of a Franciscan monastery lie in the remote Sintra hills awaiting exploration.

Following the trail of an old metro line, this scenic path is haunted by a creepy spriggan statue.

Some call this eerie forest of crooked trees the "Bermuda Triangle of Romania."

The 19th-century ruins hide deep in an overgrown forest.

The haunting cadaver tomb of a famous French poet, playwright, and filmmaker.

The narrow mountain road that carves a path between Florence and Victor is tied to ghost towns and ghost stories.

A submerged archeological park still holds the wonders of a Roman Sodom.

A bizarre house filled with an astounding array of collections.

A lovers' beach, tucked below the surface of the island, provides a safe haven for romance.

Once the path of a railway tunnel, now home to thousands of glowing insects.

A galaxy of glowworms—larvae of a gnat—hides deep in the belly of these caves.

Bioluminescence in the reefs of the Maldives causes the sea to glow like a starry night sky.

What looks like a link in Gondor's early warning system is actually a centuries-old Italian fortress.

This picturesque mansion has gone from opulent ruin to nature museum.

A defensive fortification carved into a cliff near Sydney Harbour.

The translucent turquoise hue of these natural swimming pools comes from a high concentration of minerals.

The same water that fills a luxury resort’s pools feeds these free hot springs in the rainforest.

Costa Rican accommodation resembles a crash site, but with a nice balcony.

This neon blue river gets its color from a unique mix of bacteria and volcano minerals.

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.