2300-year-old Roman road connecting the empire.

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

Spain's unique Mosque-Cathedral has been a place of worship for both Muslims and Christians throughout its history.

A curious carving hides on a marble column in the Mosque-Cathedral of Córdoba.

A pair of gigantic baby heads greet passengers at Atocha Station.

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

Spain's largest bullring offers a unique glimpse at architecture and history.

The world's largest wooden structure.

An early 20th-century bullring converted into a modern shopping center.

The oldest giants in Catalonia are now displayed in a 14th-century Gothic church.

A vista of the city and sea from atop the little-known viewing deck on an unassuming Columbus statue.

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

Sky ships, planes, and portraits left as unique tokens of hope and thankfulness.

A crumbling island fortress that seems to be covered in a field of stone crosses but is simply incomplete.

A curious collection of locks and keys.

A font of vintage porn on the silver screen.

A museum dedicated to one of Paris’s most famous residents, tucked into a corner of one of the city’s most famous squares.

This 18th-century sundial was designed to calculate the date of Easter each year.

The tradition of open-air secondhand and antiquarian bookselling in Paris dates back to the Renaissance.

A lone cannonball remains lodged in the walls of the Hotel de Sens as a sober reminder of a revolution.

This museum in a Paris apartment gives a unique look at the iconic French singer's life.

Noirish green neon marks the location of one of the oldest private detective agencies in France.

A modern-day Lascaux cave underneath Paris.

A museum on the history of Paris, including a set of Napoleon's toiletries, Proust's room, and relics of the Revolution.