Two very green residential towers cleaning the air in one of Europe's most polluted cities.

A miniature village mimics the surrounding buildings so well it includes itself.

This medieval sanctuary's tree-framed door looks like a portal to a mythical realm.

Putting the "mod" in "modular" since 2000.

A musical composition 1000 years in length plays at the Trinity Buoy Wharf in London.

A monument to the thrice mayor of London who according to lore made his fortune by selling his rat-chasing cat.

The commemorative stone column conceals a secret laboratory.

A hidden treasure in London with a rich medieval history, and the resting place of many luminaries.

A discarded movie prop that was the original monolith for "2001: A Space Odyssey."

This unassuming alcove in London’s famous Tower Bridge once served to capture, store, and display dead bodies from the River Thames.

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

A miniature Italianate fantasy village on the coast of Wales and the set of ITC classic "The Prisoner."

When it came to designing his own small office building, the eccentric architect wasn't afraid to show the world what he could do.

A 15th-century former coaching inn forms the implausibly grand entrance to a 1980s shopping mall.

These 90-year-old murals of local kings, Vikings, and outlaws hide in plain sight in a beautifully baroque shopping arcade.

The biggest and deepest Cold War bunker open to the public can be found in southeast England.

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

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

This 19th-century Turkish bath house survived the Blitz of London and is now an events venue.

You won't find these curiously named passageways anywhere else in England.

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.

The bar where "The Great Train Robbery" was planned was once a nexus of high society and low morals.