In the fictional world of Kcymaerxthaere, celestial wonders marked a portal to a powerful route of travel at this site in Madrid, Spain.

An architectural oddity hides in plain sight on this iconic London bridge.

The secret wartime bunker built on the platforms of an abandoned Tube station.

Six ravens are kept captive (but well-fed) at the Tower of London to prevent the fall of the Crown.

A collection of comics, graphic novels, animation and caricatures devoted to exploring this often overlooked art form.

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

An unusual round church in London with a Templar past.

One part local history, 99 parts gruesome haunted house.

This London pub hides a peculiar secret: a recreation of the rooms shared at 221b Baker Street by Sherlock Holmes and Dr. Watson.

Eighty million natural history specimens call this gargantuan museum home.

Banksy gives themself artistic license with this piece of London street art.

The popularity of Sherlock Holmes led to the creation of his fictional address, turning the orderly London street numbers askew.

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

A charming 17th-century alley is lined with secondhand bookstores and antiquarian shops.

Kings Cross Station pays tribute to its role in Britain's best-selling book series.

The last of Amsterdam's original sea level markers remaining in place.

This large copper bolt represents the benchmark for measuring sea levels in most of Europe.

Europe's official "zero-level," the equator of elevation.

A public urinal so pretty, it was declared a national monument.

Three connected pink triangles memorialize persecuted gays and lesbians throughout history.

Museum preserving torture methods from the past.

This effigy of Peter the Great is greatly disproportionate.

Perhaps the tiniest sculpture in Saint Petersburg is a little bronze finch inspired by a song.

Once frequented by heavyweights of the Russian arts scene, this café is stuck in the 1800s.