The New York hotel where tragic visionary Nikola Tesla spent his final hours, destitute and alone but for the pigeons.

Below a historic English market town lies a secret underground city complete with kitchens, laundries, storerooms, and an underground lake.

An archaeological site believed to be the burial place of the "mother of us all."

A good place to research the Freemasons, esoterica, occultism, and hermeticism.

Come for the pastrami, stay for the million-dollar art.

Rivers of cattle blood gone, a strange Escheresque building remains, the last of its kind.

Yale University's home for rare works, including the mysterious Voynich Manuscript.

Stockholm's decidedly unique public transit system has doubled as the world's longest art gallery for decades.

Pilgrimage site for star-crossed lovers.

A gruesome memorial for those lost in this area during the Khmer Rouge genocide.

An old town theater converted into a celebration of the hobo legacy.

Enormous underground chamber built to detect 'ghost particles' of the universe.

Venice's "Island of the Mad."

A lovers' beach, tucked below the surface of the island, provides a safe haven for romance.

The abandoned Japanese amusement park once loomed as a dystopian Disneyland.

A Museum of Holography frozen in 1974.

A treasure trove of pathological, forensic, parasitological, and anatomical specimens.

Myanmar's Mount Olympus atop a 2,500-foot volcanic plug.