This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

A historic house left in "dramatic still life."

Preserved behind glass, the ruins of a medieval building used to store human remains.

Tucked away in the Tower of London is the weapon once used to execute high-profile prisoners.

It celebrates a very stinky task and salutes London's fatberg-vanquishing team.

A historic London cemetery now serves as a nature park incorporating gravestones & memorial statues.

Where condemned pirates met their grisly end at the gallows on the River Thames.

This uncanny fresco celebrating the "triumph of death" was split into four pieces to be moved to another museum.

Where Aleister Crowley taught magick in "La Chambre Des Cauchemars," his "Chamber of Nightmares."

A medieval wash house where people washed clothes in a river allegedly formed by the tears of a mourning nymph.

Cave shrine on Monte Pellegrino.

A mysterious ancient elephant said to possess magic powers is now the symbol of a Sicilian city.

Behind medieval walls in a corner of bustling Palermo is a breathtaking former mosque once inhabited by a wolf-taming hermit.

This mosaic-lined medieval church was built by the world's first admiral and still holds mass in ancient Greek.

Thousands of well-dressed mummies below a monastery.

The burial place of an obscure North African saint was turned into a macabre body preservation factory for the 17th-century Neapolitan elite.

The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

The relics of dozens of martyrs are stored in a single chapel.

A hidden network of subterranean passageways lies tangled beneath Indianapolis' bustling City Market.

A labyrinthine underworld of tunnels and caverns hides beneath the city.

A labyrinth of ancient tunnels hidden below the city holds the ruins of 2,500 years of history.

An underground paleo-Christian burial site composed of the remains of several cemeteries and Basilicas.

A labyrinth hides in plain sight at each of the city's 270 Tube stations.

Pop culture has helped to keep this iconic British building from being destroyed.