The final resting place for the remains of 143 Habsburg royalty.

Enjoy an overnight at an old haunted B&B site of the Borden family murders.

Home to the largest urban bat colony in North America, estimated at 1.5 million bats.

A marvel of Byzantine engineering under the streets of Istanbul.

Two thousand artifacts from around the world collected by one woman who loved to travel.

The 953 windows undoubtedly make this the world's most beautiful screened porch.

An eccentric inventor's castle home with its own indoor weather system.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.

The popularity of Sherlock Holmes led to the creation of his fictional address, turning the orderly London street numbers askew.

The second-largest cave chamber in the world was discovered in 1898 by a 16-year-old and a friend known as "Pothead."

A museum dedicated to exhibiting remarkable outsider art.

The trials and tribulations of marking Poe's grave.

The hallucinogenic center of the ancient world.

The celebrated eyesore created by starry-eyed sweethearts.

Roman ruins top white travertine terraces formed by ancient hot springs.

A sprawling Baroque park with 300-year-old hydro-pneumatic waterworks.

A 300-year-old tea shop that brought tea to the English people, not to mention the Queen herself.

Home to items never before seen by the public.

Tour the dark and beloved poet's former cobwebbed basement, which may have inspired "The Black Cat."

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

Explore the largest pure gypsum deposit in the world, and go dune sledding while you're at it.

The world's longest known cave system.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.