This mansion oasis contains gardens, sculptures, and fountains just off the busy Plaça Kennedy in Sant Gervasi.

Final resting place of one of the classic authors of horror literature.

Last residence of H.P. Lovecraft featured in his story "The Haunter of the Dark."

The mass grave of a heroic Revolutionary War regiment sits below an empty lot near the Gowanus Canal.

In its day this historic fort held 100 cannons pointed in almost every direction to protect New York.

On the wall of this medieval walkway, a symbol of the Spanish Inquisition.

Underground vaults of a former brewery beneath Brooklyn's Crown Heights are now used to ripen cheese.

Two 2,500-year-old Phoenician boats found on the coast of Spain, giving incredible insight into the ancient maritime traders.

Holding the most bodies of any cemetery in the United States.

A beautiful but toxic fountain of mercury.

An ancient Egyptian temple in the middle of Madrid, Spain.

Come for the chanting, stay for the monastical vegan buffet.

A once-secret library of Freemason history in Catalonia.