The celebrated eyesore created by starry-eyed sweethearts.

William Smith's iconic "map that changed the world" is hidden behind a curtain in the Geological Society building.

This overlooked street light once served as a KGB dead letter box.

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

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.

This neon landmark has been posing this deadpan question to follicly-challenged Dubliners for over 50 years.

Experience what life was like in Ireland during the Viking and medieval ages.

The enchanting archway is the only surviving portal into Dublin’s lost medieval wall.

The oldest public library in Ireland.

The modern birthplace of Irish freedom.

Dublin's most modern, visually spectacular bridge is modeled after Ireland's national emblem.

The wooden telephone box hidden away in London's Piccadilly was the original prototype of the iconic kiosk.

This London plaque marks the spot where David Bowie's famous alien made his debut.

Bronze sculpture celebrating the relationship between Churchill and Roosevelt.

This luxury shopping lane has been protected by its own tiny police force for over a century.

Never actually a tree at all, this spot was the site of London's public hangings for nearly 600 years.

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

A unique tribute to the millions of animals who served and died for the British military.

This legendary stone is of unknown origin, and throughout history has been a literal touchstone for British leaders.

This museum tucked below a charming cafe gives a brief snapshot of photographic history.

A mysterious pair of mice eating a piece of cheese is London's smallest public sculpture.

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

The 2,000-year-old beam is tucked within the pedestrian entrance to the old London Bridge.