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

A friendly pub with a sordid past in cock fighting.

Rebuilt remains of a temple to Roman god Mithras.

London's amazing modernist public square that never was.

The Great Fire of London and the regulation of one-way streets both started in this alley.

The commemorative stone column conceals a secret laboratory.

The bridge is a secret gallery of discarded gum that has been transformed into miniature masterpieces.

This lonely bronze walrus celebrates a character in a Lewis Carroll poem.

A museum and gardens with unusual plants and a history of progressive programming for the blind.

One of England's oldest stone churches and the birthplace of the "father of English history."

This steel sculpture made from a recycled crane towers above a former shipyard.

An enigmatic sculpture depicts a ruined home with debris stretching for over half a mile along the river.

An abandoned tower once used to study the cosmos hides within a thicket of greenery.

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

This unique bridge curls up like a caterpillar to let boats pass and then unfurls again to span a small canal.

The bronze uniforms commemorate the vital role of women during World War II.

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

These official units of measurement—including chains and perches—lie hidden beneath tourists' feet in a popular London hub.

A haunting monument dedicated to the Royal Naval Air Service and the Fleet Air Arm.

A statue of the legendary Celtic warrior queen who fought the Roman invaders stands in one of the cities she once destroyed.

Claiming to be the oldest hat store in the world, this historic haberdashery had a hand (and a head) in the creation of the Bowler.

An alleyway plaque is all that remains of the independent Texas' envoy that forgot to pay their rent for over a century.

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

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