A tiny, unassuming park in Tampa that belongs to the Republic of Cuba.

An underground magnet for ever-changing street art.

An immersive environment that is part haunted house, part choose-your-own-adventure, and part jungle gym.

The installation’s official name, “You Who Are Getting Obliterated in the Dancing Swarm of Fireflies,” says it all.

This futuristic German spa allows visitors to float in a pool of salt water while zoning out to underwater techno.

A tour of underground Berlin takes you through WWII air raid shelters and tunnels used to smuggle people out of East Germany.

A whimsical and twisted animatronic monster tour beneath the streets of Berlin.

Resting place of Hollywood's immortals is also site of summer film screenings.

Hitler's bleak vision of relaxation still stands as a mostly abandoned 10,000-room resort complex.

A haunted hot springs hotel that went from healing retreat to asylum before it was restored.

Built by the inventor of the radio, this abandoned hotel has housed early radio employees, military men, and a dangerous cult.

The top of society once luxuriated in this world-class hotel, which continues to impress, even in ruin.

A once-luxurious, now abandoned hotel in the Italian Alps.

The decaying remains of a once-luxurious Soviet spa town.

An abandoned hotel in the highlands of Bali is shrouded in stories of ghosts, curses, and corruption.

The remains of a failed attempt at medieval nerdery are hidden deep in the woods of Virginia.

A well-preserved Ancestral Puebloan ruin tucked beneath a desert cliff.

This crumbling UFO is one of only a few remaining "moveable ski chalets" of its kind.

The location of Puerto Rico's first water bottling plant, thanks to a collaboration between Mother Nature and technology.

An abandoned relic of the city's failed experiment with below ground transit.

Tucked away on an empty wooded lot in suburban Oklahoma City lie the remnants of an abandoned circus camp.

This road in the Great Smoky Mountains was supposed to assuage a displaced community, but ended up a $52 million dead end.

A crumbling hospital from the 1850s on Roosevelt Island.

Hidden in plain sight on the Hudson River is an abandoned train station where nature has taken over.