At this Denver landmark, the meals are compulsory, the sopapillas are complimentary, and the insanity is everywhere.

This massive subterranean fissure is known as the "underground Grand Canyon."

This immaculate and historic water garden culminates in a massive stone dining table with an inset fountain for chilling the wine of the Cardinal's guests.

The liveliest ghost town in the state.

Ancient paintings known as the "Sistine Chapel of Cave Art."

A trio of hidden hot tubs takes advantage of Iceland's natural geothermal vents.

Sacked by Vikings, blessed by William the Conqueror, dealt a fatal blow during the French Revolution—these ruins have seen it all.

The heads of two giant mythological water horses honor Scotland's horselord past.

Collection of trolley cars in the woods represent one man's attempt to preserve transportation history.

A closed London rail station created to cart away the dead still bears the marks of attempts to make it less morbid.

A once-booming Mississippi River town with a history of racial violence is now eerie and mostly abandoned.

This legendary "evil" doll has been haunting the citizens of Key West for over 100 years.

The mortal remains of an estimated 70,000 people lie in the basement of a monastery in Lima, Peru.

A mysterious light floating in the trees of Arkansas may be a piezoelectric effect.

Trick water gardens from 1619 featuring a 200 piece mechanical theater powered by water.

A 19th-century subterranean reservoir repurposed as a contemporary art cave.

One of the steepest streets in the United States makes an intriguing challenge for cyclists.

This "floating railway" is one of the world's oldest monorail systems.

The ruins of a Duke's bucolic dream, where camels once roamed alongside "Dutch" windmills and faux-Italian vineyards.

The highest peak in the United Kingdom has a history of physics, specters, and a pilgrimage of strange objects.

The engineering wonder and pleasure dome of a much-maligned emperor still holds undiscovered secrets.

These ominous lava formations were said to be an entrance to the netherworld so of course they inspired a famous metal band.

Created hundreds of years ago, the magical follies and landscapes at this park were almost lost to time before being restored.

A subterranean playground in an abandoned slate mine.