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

A grand imperial capital left to fall into magnificent ruin.

This picturesque ghost town is located on the banks of the Suwannee River.

The ruins of a Florida miracle spring resort make it seem like a wonder that this was ever a health spa.

Hide from the tourist hordes in these relatively unknown, and unguarded lava caves.

A unique seaside cave where Aleister Crowley faked his own death.

A humid oasis combines recreation with exploration in a unique underwater cavern.

This once bustling boomtown hotel is now the hottest spot in Nevada for ghost hunters.

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

Enchanting cave with a river crashing through the roof.

This tiered waterfall is so pretty it may cause visitors to cry tears of their own.

A limestone wonderland of water and subterranean secrets.

The so-called "world's shortest river" is actually a window into a cave.

This frequently-photographed waterfall takes only a short hike to visit.

One man has installed bathtubs into the Utah desert floor to harness the powers of a natural hot spring.

Half of a waterfall goes into the river while the other half seems to disappear.

These Great Lakes sea caves accessible by boat in the summer turn into temples of ice reachable by foot in the winter.

This trio of Dominican cave lakes comprise a colorful biosphere of natural life.

The true depths of these stunning Moroccan caves are unknown.

Discovered by cows, these upstate New York show caves are presented with a healthy dose of psychedelic folk art.

Sail through this subterranean show cave that is home to a legend that would go on to name nearly everything around it.

Semi-precious Blue John stones have been mined in this cavern system for centuries.

What was once the largest mine in North America has left behind a hollow hill filled with bright blue waters.

A subterranean playground in an abandoned slate mine.