The name of this ancient Indonesian temple translates as "Elephant Cave" but it could be more accurately called "The Hellmouth."

This Toronto garden collects stares and tchotchkes in equal measure.

This legendary "evil" doll has been haunting the citizens of Key West for over 100 years.

Exquisite wall sculptures carved in secret by an early quarryman in an obscure corner of the Paris Catacombs.

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

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

A mysterious artist-run cabinet of curiosities and library.

A burial ground of rusting metal grave markers.

The abandoned "Ghost Mansion" was left to decay in the mountains of Northern Italy.

Natural cathedral designed by Italian artist Giuliano Mauri.

A 19th-century shrine covered with prosthetic body parts as votive offerings.

The Australian lorikeets that like to tie one on in an annual drinking binge.

A castle hand-built by a Spanish dreamer in the Australian tropical jungle.

This sacred cave temple is home to thousands of bats and according to legend, a giant snake king.

Visiting dignitaries and Hollywood stars once stayed at this 1920s hotel, alongside ghosts that are said to haunt its corridors.

This vast, water-filled underground labyrinth can only be toured by boat.

A boat ride through utter darkness, lit only by headlamps, reveals an emerald green pool locals believe is sacred.

These azure waters were thought to lead to the Mayan Underworld.

This replica stave church looks like a piece of Norway was simply plopped down in South Dakota.

Thanks to a loophole in property ownership, this alleyway has become a cacophonous street gallery.

A luxurious 1880s hotel with its fair share of Tiffany stained glass, Edison electricity, and of course, ghosts.

A former mental hospital founded in the 1930s by a eugenicist who advocated for the forced sterilization of patients.

This historic mansion was built as a symbol of love between a husband and wife.

A railroad tunnel that, upon its completion, was considered one of the engineering marvels of the modern world.