A naturally beautiful, seemingly bottomless deep blue spring.

These "bridges" help confused bats cross the road.

It is said the legendary wizard once lived in this sea cave beneath Tintagel Castle.

A island reachable by a causeway at low tide is possibly one of the earliest Western European locations to be identified in text.

The most loyal of little dogs, or a Victorian era publicity stunt?

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

A network of concealed passageways lies within a busy London Underground station.

You'd never know the houses at 23-24 Leinster Gardens were fakes—until you see the train tracks on the other side.

The pioneer of psychoanalysis spent the final year of his life here, still seeing patients on that famous couch.

This artist's home turned gallery/museum preserves the creator's love of "Eastern" influences.

Pop culture has helped to keep this iconic British building from being destroyed.

The Metropolitan Police refurbished the blue box (perhaps not coincidentally) the same year "Doctor Who" returned to TV screens.

London's last remaining public soapbox site has seen speeches from Karl Marx, Vladmir Lenin, and George Orwell.

The sixth of London's "Magnificent Seven" cemeteries, and a source of unlikely inspiration to Beatrix Potter.

Scattered throughout London are ancient remnants of the city's former bounding wall.

A Victorian natural history and ethnographic museum with wonderful turn-of-the-century, science-book-esque evolution displays.

Eighty million natural history specimens call this gargantuan museum home.

The world's first underground farm is in a World War II bomb shelter beneath the streets of London.

The curios of pharmacist and collector Henry Wellcome.

A hands-off space for graffiti artists to hone and display their skills.

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

The last working windmill in the U.K. that has eight sails.

A quartet of rusting satellite goliaths are all that remain of a communication network that protected Britain from German and Russian air strikes.

Amsterdam's former hotspot for public executions and dissections.