One of Scotland's most important modern structures, it just made the '100 Most Endangered Sites' list.

Old-fashioned knowledge and modern engineering create the world's only rotating boatlift.

The heads of two giant mythological water horses honor Scotland's horselord past.

Accessible only at low tide, the deserted island is dotted with World War II ruins.

Come face to face with the ferocious visage of the serpent-headed mother goddess of the Aztecs.

Once home to an aristocratic family and a workers' organization, this intricately tiled building now houses a chain restaurant.

Many people don't realize there’s a lot going on in—and below—the world’s tallest triumphal arch.

This incredible college library is a visual masterpiece of mosaic art. It also looks kind of like a giant boombox.

Mexico City's largest market contains a Willy Wonka-esque wonderland.

Visiting this cacophonous collection of vintage novelties is like stepping into the mind of a crazed toymaker.

A jaw-dropping "megalibrary" that turns book-browsing into a geometric adventure.

Frida Kahlo's childhood home, now a museum of her life and works.

A Trabant car, a kangaroo statue, and a plethora of plants take over this abandoned-factory-turned-bar.

Museum dedicated to the terror regimes of Hungary.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

Elevated freight railway turned wildly successful urban park.

Renaissance hospital featuring a rotating door into which unwanted babies were dropped.

A forgotten "city of water" underneath the famous Trevi district.

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

A new sculpture calls attention to climate change in the centuries-old city it threatens.

Two stone columns flank the grand Venice square, but there were supposed to be three.

Go inside to really appreciate this 500-year-old technological masterpiece.

Venice's "Island of the Mad."