The engineering wonder and pleasure dome of a much-maligned emperor still holds undiscovered secrets.

A 19th century artistocrat's mansion, turned into a library, hidden in a modern library.

Once the home of a hermetic monk, this cave now houses a small church.

Colorful power station with a chimney equipped with a gallery for exhaust monitoring equipment.

The world's most important buildings shrunk to a tiny size.

This community on a small Venetian island has taken to painting their houses in bright neon hues.

A small island less than half a mile from Venice is a forbidden island with a dark and twisted past.

Perfectly preserved ancient monastery in an impossibly dramatic location on a rocky island in the Atlantic.

One of the largest caves in the world open to the public.

In the woods of New Jersey lie the ruins of a munitions village abandoned after World War I and the remnants of a 1920s wooden racetrack.

An architect transformed this abandoned cement factory into his castle-like workshop.

This sword isn't waiting for a king to pull it out. It was placed there by a saint.

These medieval skyscrapers dominate the skyline of this small Tuscan town.

These gutted monastery ruins still stand proudly in the middle of the Italian countryside.

A dismembered holy head stares out from her beautiful reliquary at the St. Dominic Basilica.

An ossuary built in 1210 to collect bones from the Ospedale Maggiore of Milan.

A once-luxurious, now abandoned hotel in the Italian Alps.

One of the world’s smallest bars, just 13 square feet, is brimming with speakeasy flair.

An ancient artistic garden parlor full of hidden water wonders.

A church filled with the bones of hundreds of virgins martyrs—or so they say.

A space dedicated to contemporary art and culture, co-chaired by fashion icon Miuccia Prada.

Small on the outside, big on the inside, this church is an astonishing act of visual deception.

Gilded heaven for philatelists and architecture freaks, still in full working order despite sitting atop tremulous ground.

A jewel of the Mexico city skyline now slowly crumbles after surviving an earthquake.