Historical etchings such as “Miserable, wild, distracted 1350" and “The Archdeacon is an ass.”

Man-made cave with enigmatic carvings, some say made by the Knights Templar themselves.

This massive collection of British military artifacts includes the heartbreaking personal letters of the men in the trenches of WWI.

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

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

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

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

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

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

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

Christ's blood preserved in a Belgian town.

This former Masonic lodge has been transformed into part museum, part bar, all awesome.

Hidden in a Scotland museum is a copse of extinct tree stumps.

A scattered trail of street art adds a pop of color to the city's stark structures.

"Respectful to the dead, safe and sanitary to the living, dedicated to the Genius of Memory..."

This series of Scottish caves has no clear purpose other than baffling historians.

Accessible only at low tide, the deserted island is dotted with World War II ruins.

17th century streets hidden under Edinburgh were once a breeding ground for the black death.

An ancient passage filled with stalls selling used books, once frequented by Vincent Van Gogh.

The attic of a four-century-old canal house hides a clandestine church.

A floating cat sanctuary on an Amsterdam canal.

Cat art as far as the eye can see.

An Amsterdam street lined with antique shops each one dedicated to a different obscure collection.

Museum preserving torture methods from the past.