Behind this beachfront shop lies a spectacular, colorful sea cave with an equally colorful past.

Once the grandest synagogue in medieval Spain, it now stands as a memorial of the 15th-century Jewish exile.

The fragmented remains of a massive public bath connected to the city's water supply.

The ruins of an ancient stadium that hosted gripping chariot and horse races.

The world's oldest bookshop still in operation.

Part of the medieval watchtower is displayed in an otherwise ordinary parking garage.

Stuck in the middle of a modern Madrid city block are the remains of a 19th century sports complex.

Madrid's last horchata kiosk is a blue-and-white beacon of refreshment.

Among the oldest structures in Madrid, these Moorish walls once guarded the medieval city of Mayrit.

Come for the waffles, stay for more waffles.

America's oldest Eastern European synagogue provided the immigrants of crowded Lower East Side tenements a space of sanctuary.

This semi-hidden Manhattan restaurant is based out of a loading dock.

A dark, dank room in subterranean Manhattan was the site of a ghastly murder.

A room in New York City that contains 250 cubic yards of dirt worth a million dollars.

The world’s oldest and biggest bookstore stocking only mystery, crime fiction, espionage, and thrillers.

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

The only home that Alexander Hamilton ever owned has a history almost as troubled as his own.

Peek through the gates at this oasis from the city, full of Old English charm.

Amid the bustle and noise of the Financial District hides a secluded garden oasis above the city streets.