While most wind tunnels test scale models, the "Cave of Winds" was large enough for actual airplanes.

Washington's iconic carousel has a nice piece of Civil Rights history.

The most accurate timepiece in the world.

The first purpose-built art gallery in the United States is once again open as a center of craft arts.

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

This unreal Portuguese palace looks as though it's made from a pile of different castles.

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

Elaborately carved to showcase the glorious wealth that the age of exploration brought to the Portuguese empire.

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

The world's oldest bookshop still in operation.

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

Elaborate tile work in this railway station tells the story of Portugal.

A hidden three-foot-wide house separates these two regal churches.

The stunning interior of this Gothic church is covered in ornate gold details.

A little sculpture with a large wardrobe.

Cozy basement bar sports an inventory of over 2,000 beers.

This collection of over 50 murals celebrates Brussels' rich history as the self-proclaimed home of the "comic strip."

The video game-themed street art first popped up in the French city.

An immersive projection art installation uses sound, scale, and light to take visitors inside classic works of art.

A Parisian exterminator's shop whose storefront displays stuffed rats hanging from traps.

Twelve grave-faced marble angels guard the emperor's tomb at Les Invalides.

A Parisian cemetery where the elite and artistic are interred beneath an eccentric collection of tombs.

This charming cobbled backstreet is the most Instagramable street in Paris, much to the residents' annoyance.