A scandalous Art Nouveau collaboration that set Paris all atwitter at the turn of the century.

High atop the Eiffel Tower is a small apartment built exclusively to entertain the science elite and make the rest of Paris jealous.

One of the oldest medical collections in Europe focusing on rare surgical instruments.

This massive library holds what was once the largest book collection in the world.

This cemetery features modernist statues as strange as its name.

Mountain where Jesus was first tempted by the Devil.

Barcelona's historic 19th-century sewers, whose foundations were laid in medieval times, are open to the public for exploring.

An unusual stroll through gentlemen's erotica demonstrates that pornography is timeless.

This semi-secret storybook hedge maze is also the oldest garden in the city.

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

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

This classic restaurant features a gorgeous mirror-clad room.

This jaw-dropping 19th-century bridge uses its reflection to form what appears to be a perfect circle.

This medieval castle overlooking the Elzbach river looks just like it did hundreds of years ago.

The hometown of a beloved manga artist created a treasure hunt for his popular ghostly characters.

Some call this eerie forest of crooked trees the "Bermuda Triangle of Romania."

While exploring the desert, you can stop by the home of a fictional heretic from a parallel universe.

The most unique castle in all of Southern California, entirely constructed from repurposed materials.

The quirky salon doubles as a retro museum run by the world's leading "hairstorian."

Hundreds of trees made from glass bottles make up this forest on Route 66.

The Citrus Variety Collection at UC Riverside contains two trees of each of the 1,000+ varieties of citrus.

This unlicensed collection of fast-food memorabilia sits on the site of the first ever McDonald's restaurant.

Mexican food and folk art.

The Hopi-style structure was built by the man who discovered Desert Hot Springs' famous mineral water.