An opulent testament to the boom-and-bust history of industry in north central Indiana.

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

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

A counter-culture bookstore like no other hides in plain sight in the streets of Paris.

This 1,300 year old monastery built atop a single rock was once only accessible depending on the whims of the tide.

France's most famous cemetery, with some of its most curious tombs.

Famous landmarks and structures from across Italy fill this miniature park.

This eclectic sanctuary is a hodgepodge of various architectural styles, all crammed into one building.

A rooftop restaurant hides in plain sight atop Vienna's Palace of Justice.

This Roman amphitheatre was also the location of the first gladiator school.

This monument to the victims of a tragic explosion is said to turn and look at passing cars.

The largest underground church in Europe.

A tiny, forgotten park of surrealist sculptures in Angouleme.

A moody and picturesque riverside ruin overgrown with vegetation.

A secret door leads to this cozy dive that sells only “milk.”

Remains of the lost church hide beneath this Spanish Parliament building.

After years of slow decline, a derelict Gothic castle is now being restored to life.

This limestone outcropping was once a ceremonial site for ancient Native Americans.

One of the greatest maze designer’s greatest mazes.

A peculiar mansion built by the troubled heir to the Winchester Rifle Company fortune.

This eccentric folly house was designed by Romanian thinker Bogdan-Petriceicu Hasdeu, with a helping hand from his deceased daughter's spirit.