Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.

An existential riddle in the world's largest ancient castle.

An enormous and lavish Gothic church in Czechia.

A church of bones, decorated with 40,000 human skeletons.

An ossuary built in 1210 to collect bones from the Ospedale Maggiore of Milan.

A brutalist gem towering over the heart of Milan.

Small on the outside, big on the inside, this church is an astonishing act of visual deception.

Third time's a charm, or in this case, two testicles are.

A contemporary art installation housed within a Gothic cathedral.

Perhaps the most spectacular grotto along the Algarve coastline.

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

The popularity of Sherlock Holmes led to the creation of his fictional address, turning the orderly London street numbers askew.

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

A monument to the thrice mayor of London who according to lore made his fortune by selling his rat-chasing cat.

A story of cutlasses carelessly carving a celibate centenarian's cemetery stone.

A magnificent menagerie of oddities, including taxidermy cryptids.

This charming, narrow-gauge railway in the Thames Estuary is sometimes referred to as the "Train to Nowhere."

An 11th-century Viking gravestone in a Victorian parish church graveyard.

Largest lake in Great Britain measured by surface area.

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

An 18th-century religious argument etched into stone.

In the depths of Glasgow Cathedral's crypt, one pillar stands out from all others.

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

A sweet symbol marks the place where torturous executions were once carried out.