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

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

A cluttered and astounding collection of antiquities and curiosities.

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

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

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

An incarceration museum on the spot of possibly the oldest prison in England.

The anatomical-pathological collection of a man who changed surgery.

In this cobwebbed old operating theater, you can practically hear the screams of the unanesthetized patients.

Catacombs turned marketplace.

A hands-off space for graffiti artists to hone and display their skills.

Several plaster noses are hidden in plain sight around London's Soho neighborhood.

The curios of pharmacist and collector Henry Wellcome.

The quaint little store that is said to have inspired a famous Dickens novel was only given its name after the book was released.

An unusual round church in London with a Templar past.

A 1,215-foot tunnel transports pedestrians beneath the River Thames.

One part local history, 99 parts gruesome haunted house.

A student driver's nightmare.

Eighty million natural history specimens call this gargantuan museum home.

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

Hidden beneath the streets of London is a secret subway that only carried mail.

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.

A 300-year-old tea shop that brought tea to the English people, not to mention the Queen herself.