A Roman spa buried deep beneath the City of London.

This coffee shop lies hidden beneath a historic church.

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

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

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

A little slice of Japan and its aesthetics in London's Holland Park.

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

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

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

Drink your espresso at a Victorian-era urinal in this underground-restroom-turned-coffee-bar.

The Columbia Road Flower Market is now open every Sunday, rain or shine.

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

This one has sailed five times as far as Sir Francis Drake's famous ship.

The ritual has been performed uninterrupted for nearly 700 years.

The watery entrance for condemned prisoners heading to the Tower of London is still visible along the Thames.

The pretty iron lamp is a reminder of the architecture underneath London's streets.

These fantastically named natural pools look like something out of a Scottish myth.

A double cantilever system bridge that was designed to prevent flood damage.

Scotland's only funicular railway is also the United Kingdom's highest.

The highest peak in the United Kingdom has a history of physics, specters, and a pilgrimage of strange objects.

Now famous as the "Harry Potter bridge," this impressive concrete viaduct has long been an icon in its own right.

A former coastal watch post has been turned into a bothy with unrivaled views of the sea and its inhabitants.

Though difficult to access, this stunning cave has a place in Scotland's poetic history.

One man spent 10 years building a spectacular section of road because no one else would.