This silent sentry in the crypt below a large Gothic cathedral is often knee-deep in water.

A rare wooden coffin set vertically into the Gothic arch of an ruined church.

Under a church hides a forgotten 13th-century ossuary containing the remains of around 2,500 people.

A mysterious bridge over a sunken Roman road.

Architectureal fantasy quarter of Rome.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

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

A mysterious artist-run cabinet of curiosities and library.

The bar where "The Great Train Robbery" was planned was once a nexus of high society and low morals.

This replica Viking village was created for a film that was never shot and is now open to visitors.

This floating garden in the sky is straight out of a fairy tale, but the real thing is nothing short of magical.

A proud bronze billy stands as an eternal symbol of Ireland's oldest festival, where a goat is made king.

Hear the quietest sound from across the dome.

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

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

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

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

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

Traveling collection of amazing automata.

Shakespeare, David Bowie, Dr. Who, the Saxons, Druids and Romans are all claimed to have all made their mark on these massive man made tunnels.

Surreal riveted sea forts once protected the Kent shores from German attack.

A house of bones — but nobody is quite sure to whom they belong.

"In the Dark" Restaurant in Paris offers dinner in complete darkness.

A historic house devoted to the teachings of a 1700's prophetess and her mysterious box of revelations.