World's first "penitentiary," meant to be humane, drove men insane.

Over 100 concrete munitions bunkers are all that remain of a Pennsylvanian village seized by the US government.

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

A peculiar mansion built by the troubled heir to the Winchester Rifle Company fortune.

A bit of retro transportation flair preserved in the world's largest department store.

These historic defenses ensured the city within would survive hundreds of years of occupations, sieges, and invasions.

Vacant Beaux-Arts buildings that serve as reminders of a beach town’s glory days.

The former home of the Nobel Prize-winning American writer is now home to dozens of six-toed cats.

A monument celebrating the idea of reaching inaccessible places.

The last remaining relic of San Francisco's glittering 1915 Panama Pacific Exposition.

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

Filled with goldfish swimming in a shallow pool of sea water, this ancient crypt is more wishing well than burial site.

The once forbidden "secret cabinet" of erotic art from excavations of Pompeii and Herculaneum.

A 250-year-old timepiece-automaton adorned with golden mechanical birds, which still sing to this day.

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

The celebrated eyesore created by starry-eyed sweethearts.

An ancient knight and a symbol of the city's freedom.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

Baroque celebration of the end of the Great Plague of Vienna.

America's most famous museum of medical oddities is home to the remains of Albert Einstein's brain.

A church of bones, decorated with 40,000 human skeletons.

The final resting place for the remains of 143 Habsburg royalty.

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