The morbid items in this small and hidden museum are not for the weak stomached.

This automated sculpture of two men peeing will spell out text messages with their micturition.

The hidden lair of an alchemist rediscovered in a 2002 flood.

Two stunning 17th-century libraries and a cabinet of curiosities.

Countless grotesque faces stare out from this eerie Prague art wall.

A Jenga-style cylindrical tower of books that appears to go on forever.

The remains of the great moral philosopher reside in a university in London.

This coffee shop lies hidden beneath a historic church.

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

A community of artists and entrepreneurs seeks a simpler life on London's waterways.

A relic of Victorian grandeur hides beneath a busy South London road.

A Roman spa buried deep beneath the City of London.

This secluded walkway overlooks a magnificently wild London green space.

An artistic tribute to the famous singer, just around the corner from where he was born.

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

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

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

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

The curios of pharmacist and collector Henry Wellcome.

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

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

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

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