Part of the medieval watchtower is displayed in an otherwise ordinary parking garage.

A reproduction of the famous prehistoric cave paintings is hidden underground at the National Archaeological Museum.

Stuck in the middle of a modern Madrid city block are the remains of a 19th century sports complex.

This postmodern apartment block was designed to be a vertical neighborhood.

What looks like a suicide in progress is actually a statue of Sigmund Freud.

The fences outside some of South London's estates are made from recycled World War II stretchers.

These ornate arches show how the course of the River Thames has changed.

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

This museum inside a museum tells the story of London's timepieces.

An eccentric 18th century naval officer built a ship's quarterdeck on his roof, the inspiration for Mary Poppins's "Admiral Boom."

Art Deco and “Wrenaissance” mash-up, this recently restored royal residence has been home to kings and comes with secret monkey passages included.

The "lost friend” is the most famous of the six moai statues that were removed from Easter Island.

The childhood home of Earth's alien chameleon is a humble Brixton flat.

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

The largest of London's subterranean rivers and once a mad, bad center of London life.

The final resting place to 300 Victorian-era pets hides inside the city park.

An easily overlooked stretch of ornate window fronts and gaslight lamps that could be right from the pages of Dickens.

This shop and gallery is a modern-day cabinet of curiosities, unassumingly positioned along an urban thoroughfare.

A tongue-in-cheek arcade where the games are based on everyday life.

A decommissioned tube carriage within a London museum hosts a regular pop-up supper club.

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

A kaleidoscopic warehouse-maze of handmade neon signs.

This South London cemetery holds the remains of more than 15,000 people.

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