A performance hall at the American Jewish University moonlights as a sci-fi film location set.

One of the oldest reform schools in the United States, home to wayward boys such as Merle Haggard, now abandoned.

A hospital closed seemingly in the middle of operations, leaving behind fodder for horror films and ghost hunters.

The beautiful 1920 Pantages Theatre remains hidden just underneath the LA Downtown Jewelry Exchange.

This opulent hotel has been visited by Spider-Man, Charlie's Angels, and the Ghostbusters.

Originally the home of chewing gum mogul William Wrigely Jr, it is now the official offices of the Tournament of Roses.

Hidden in a grotto 26 feet below Nottingham's oldest hotel, this stylish subterranean drinking den is notoriously hard to find.

This former stomping grounds of the most eminent astronomers of the early 20th century.

A small and surprising passageway in Saint Petersburg devoted to the Beatles.

This traditional garden in the San Fernando Valley doubled for Star Fleet Academy, and is irrigated entirely by wastewater.

The short oil boom of Venice Beach, and its swift removal from the tourism-laden landscape.

During prohibition, corrupt city officials ran drinking dens under the streets of Downtown Los Angeles.

Giant Redwood-themed cafeteria operates under the golden rule, "Dine Free Unless Delighted."

A turn of the century building boasting some of the most beautiful art nouveau architecture in Prague.

A brush maker used his factory to protect blind Jews from the Gestapo.

Eighteen miniature death-scene dioramas.

An "inside out" building in the historical center of Paris, featuring Europe’s largest modern art museum.

Named after a militant urban guerilla, this famous former squat is a graffiti-covered stronghold of leftist culture.

A massive 1830s industrial site once known as Czechia's "Iron Heart" has been transformed into a playground of science, technology, and art.

Unique house covered in a nightmarish mural of demons, ghosts and monsters.

The world's greatest slide descends 18 stories from this looping mountaintop viewing platform.

Macabre astrological automaton clock dating to the late 1400s.

The subterranean "lake" below the Paris opera house inspired the Phantom of the Opera's lair.

Egyptian Revival movie palace abandoned for decades and restored in 2013.