This gaping hole in the middle of a remote mountain lake looks like a portal to another dimension.

The mirrored section takes the shape of Hebrew characters when viewed from above.

A poignant museum dedicated to the history of the Dutch resistance against Nazi occupation

The final resting place of one of the brightest physicists of the 20th century.

The last Viking king of Denmark is buried inside the crypt of this cathedral.

Generations have refused to move this doll from its dusty resting place to preserve a castle from a watery fate.

This striking royal residence is the largest Renaissance-style castle in Scandinavia.

This Danish castle is supposedly haunted by a woman too independent to not be a witch.

Old Danish castle immortalized in Shakespeare's Hamlet.

A natural wonder in south Denmark.

This colorful artistic feature atop a Danish art gallery allows visitors to stroll through a rainbow.

This sublime architectural marvel is a rare example of an expressionist church.

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

A forgotten monument to Yugoslavian freedom.

This Croatian fairytale castle is slowly falling apart thanks to years of neglect.

This truly palatial work of Communist-era architecture now sits crumbling on a Croatian beach.

An ethereal glowing blue ocean cave in Croatia.

An enchanting monastery in the Spanish countryside appears lifted from a fantasy tale.

Wonderland replication in progress by one persistent man.

Spanning the El Chorro gorge, this pathway used to be one of the most dangerous crossings in the world.

A beautiful but toxic fountain of mercury.

A neighborhood church's unusual abstract stained glass was the final project of avant-garde artist Jean Cocteau.

Tens of thousands of ancient rock carvings hidden in the heart of a French national park.

Lyon's "Wall of the Silk Weavers" is one of the largest murals in Europe.