Unlike many reclaimed, abandoned mines, this Canadian cave system is still just a dangerous maze.

The birthplace of a titan of American cinema.

These black pillars of volcanic basalt seem to call mountain climbers with an unbreakable siren song.

"Not too many people can say they've had a nuclear bomb dropped on them, not too many would want to." — Walter Gregg.

An entire town preserved as a historic landmark.

The rocks of a certain area of Butte, Montana give off a musical ring when hit.

Mysterious rocks that ring musically when struck.

Partially collapsed lava tube and cave system complete with concert hall, underground pond, and unique albino crabs.

Last church of this militaristic WWII style.

Civil War Fort on an island in the Boston Harbor.

Final resting place of two dozen New York City harbor ships.

The final remnant of the Arkansas zinc industry is this historically protected ghost town.

High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

The neon signs from Las Vegas' past find their final resting place at this unusual graveyard.

A stoic rock cairn is all that remains to remember one of the more brutal instances of frontier treachery in American history.

A massive underwater sinkhole made famous by Jacques Cousteau.

The subtle interplay of fire and water is hard to ignore at this remote Jamaican spring.

This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.

Visit the monolithic tomb of America's most famous general.

Egyptian Revival movie palace abandoned for decades and restored in 2013.

Built to hold the worst of the worst of the Nazi war prisoners.

This "thrice-cursed" island is allegedly home to Captain Kidd's lost treasure.

Besieged by war, this castle ruin has crumbled into a peaceful picnic spot.

An abandoned colonial French prison notorious for its hellish conditions.