Built to give thanks for the passing of a plague epidemic, this cathedral is a one-of-a-kind architectural hybrid.

Op-art architecture designed for happiness.

Massive puppet-automaton machines created by French artist collective Machines de l’Ile.

The crypt of the imposing Stephensdom holds royal intestines and thousands of skeletons.

Giant WWII fortresses that fired 8,000 rounds a minute, now home to thousands of pigeons.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

This iconic Parisian bookstore doubles as the "Tumbleweed Hotel" for traveling writers.

In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

These numerous Israeli caves were dug out over hundreds years for reasons ranging from hideouts to burial sites.

The oldest housing complex in Riga is a mini timeline of architectural trends.

The maze-like transportation hub contains abandoned areas, derelict stores, and a resident bat colony.

This clock is an architectural flourish that stands out as a landmark among a unique Israeli German community.

These mechanical goats first battled it out in the year 1551, all because of an overcooked deer.

The traditional Polish croissant, folded 81 times into the shape of a horseshoe, is a legally protected cultural treat.

A 19th-century politician who died after walking home in a blizzard is honored with this Manhattan statue.

This whimsical group of statues is a favorite of children who love to climb all over Lewis Carroll's beloved characters.

This nightmarish children's plaything was left grotesque to help kids conquer their fear.

The remains of this ancient fortress atop a manmade hill look as though they were built into a volcano.

A massive, heart-shaped, wind-carved crater in the middle of the Israeli desert.

This daunting 1st century fortress was purportedly the site of one of the most dramatic revolts of the Jewish-Roman wars.

Elevated freight railway turned wildly successful urban park.

Eighty million natural history specimens call this gargantuan museum home.

This tipsy office building in downtown Prague was originally called “Fred and Ginger.”

Around 100,000 bodies are buried below the medieval headstones, many of which mark graves with multiple bodies stacked up to 12 deep.