A network of concealed passageways lies within a busy London Underground station.

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

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

This wildly-tiled artist's palace is a living and growing account of the creator's life, loves, and labors.

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

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

The site of London's first coffee house has been serving refreshments of one kind or another for 360 years.

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

A historic London pub with prison cells in the cellar and a "spy room" on the second floor.

An unusual round church in London with a Templar past.

A special shop catering to the needs of things that go bump in the night, and also helps kids become writers.

Catacombs turned marketplace.

Rebuilt remains of a temple to Roman god Mithras.

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

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

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

A student driver's nightmare.

The only university zoological museum in London houses extinct animals, bizarre natural history specimens, and a Micrarium of microscopic creatures.

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

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

This 1920s Dutch barge is now a floating bookstore.

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

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

Eighty million natural history specimens call this gargantuan museum home.