A commemorative plaque hides a door that leads down to the New York Public Library's underground book bunker.

A 2017 crowdfunding campaign saved this historic castle from being destroyed.

A 140-year-old castle with underground caves hidden in San Francisco.

Eat like a bird in a bamboo nest.

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

In the oldest zen temple stands a descendant of the very tree that introduced tea to Japanese culture.

Granny Smiths and Fujis can both be traced back to Kazakhstan, where apples still grow wild.

Once a safe haven for locals engaged in blood feuds, this 400-year-old fortified tower is now a museum showing what life was like for those lying in wait within its walls.

Inside this old mill is a collection of images that will always remain frozen in time.

A New England curiosity cabinet, one hundred years on.

Scary metal statues adorn some of the signature buildings of Burlington, Vermont.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

A treasure trove of artifacts, books, and artwork from the "golden age" of exploration.

This spooky road cut through a mound of ancient coral might be haunted by a witch.

Deceased nuns were placed on stone chairs to decompose, while the surviving nuns prayed near the lifeless bodies.

This historic, palatial theater is now one of the world’s most beautiful bookstores.

France's most famous cemetery, with some of its most curious tombs.

Once an indicator of social class, the color blue has come to define this city on the edge of the Thar Desert.

Bring your own cardboard to the slippery slopes of concrete hidden in a neighborhood park.

The world's longest continuously running show has played at this small West End theater since 1974.

The site of the climactic scene from the classic horror film is now a historic landmark.

A 16th-century horror show built in a lovely Italian garden.

These fascinating 19th-century tombs in the center of Pune belong to Europeans who lived in the city in that era.

A church of bones, decorated with 40,000 human skeletons.