A 2000-year-old Roman amphitheater lies just below Guildhall Yard.

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

Wedged between two buildings at the Great Ormond Street Hospital is this secret music installation.

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

The curios of pharmacist and collector Henry Wellcome.

Rebuilt remains of a temple to Roman god Mithras.

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

A subterranean ice warehouse that has lain hidden beneath central London for over a century is now open to the public.

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

Banksy gives themself artistic license with this piece of London street art.

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

Winding paths and ramshackle mausoleums in the oldest "park cemetery" in London.

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

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

This collection of illusory paraphernalia has been culled from the history of London's premier magician's club.

This futuristic German spa allows visitors to float in a pool of salt water while zoning out to underwater techno.