This landmark church concealed a crypt packed with bones that was discovered thanks to the London Blitz.

Wedged between two buildings at the Great Ormond Street Hospital is this secret music installation.

A cluttered and astounding collection of antiquities and curiosities.

Bronze sculpture celebrating the relationship between Churchill and Roosevelt.

The British monarchy's stamp collection is one of the most impressive in all of Europe revealing generations of royal nerdery.

The signs of a long buried road can still be found hidden beneath a London sewer grate.

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

The television series' iconic giant foot was borrowed from this classical painting.

London's smallest police station is barely the size of a phone booth.

Quaint, disturbing, and macabre objects are all on display at this intriguing collection of medical instruments from bygone eras.

A makeshift shrine to the late rock star is still kept up on the nondescript façade outside 1 Logan Place.

A quaint medieval millhouse hovers surprisingly above the waters of the Seine.

A striking 12th-century-style castle built on the edge of a cliff.

The Church of the Annunciation was carved into the face of a cliff, just like the rest of the town of Haute-Isle.

Hundreds of dwarf beeches create an unusual, haunting forest in the north of France.

The odd depiction of the Virgin Mary and baby Jesus is rooted in the Catholic Church's eradication of Catharism.

A mysterious structure left behind on the Polish mountainside, sometimes called "Hitler's Stonehenge".

An 18th-century lighthouse built on a 16th-century castle is now a monument to the maritime beacons of Scotland.

A spiral staircase twists to the top of this unusual Czech lookout tower.

A little church on a tiny island looks like something from a fairy tale.

This network of conjoined cellars was riddled with traps and supposedly allowed the townspeople to pretend their homes were deserted.

Europe's second largest ossuary wasn't discovered until 2001.

The world's greatest slide descends 18 stories from this looping mountaintop viewing platform.

Massive installation of Europe's negative stereotypes.