An abandoned set from the 1980 film "Popeye," claimed and repurposed as a theme park by creative locals.

Hidden beneath a restaurant, underground tunnels tell the story of Malta’s tragic role in World War II.

For over two centuries, this palace served as a residence for the Holy Roman Inquisition's leaders, a courthouse, and a prison.

This almost-forgotten underground dungeon housed several convicts over the years, including Caravaggio.

A century-old prison in the heart of Vilnius is now a lively bar, dance club, and artist residency.

These plaques found across Warsaw commemorate the sites where executions or battles took place during the German occupation.

These bronze horses on the gates of the Royal Palace of Naples were a gift from a Russian tsar.

This monumental fountain has moved around the city multiple times.

The Neapolitan Cult of the Dead still cares for the skulls at this mini-Fontanelle.

Richard Luke Concanen never set foot on American soil.

The sacristy of this church contains remains and relics of members of the Aragonese royal family.

This medieval city gate is now a blend of the past and the modern world.

A rococo room covered entirely in porcelain originally constructed for another royal residence.

An unusual "skull with ears" sits in the crypt of this small church tucked away at the end of a narrow alley.

This unique wooden mosque resembling a Chinese pagoda was said to be built without the use of nails.

Granny Smiths and Fujis can both be traced back to Kazakhstan, where apples still grow wild.

Hundreds of hidden passageways weave through the old quarters of Lyon.

These giant yellow bowling pins seem to be defying gravity.

For years, the remains of this ancient Roman fortress were hidden under an orchard.

It's forbidden to dig within this ancient Roman fort hidden beneath a playground.

Once housed in the towers of this Gothic church, this 17th century clock still ticks today.

The Rozenberg wind wall in South Holland makes for smooth sailing through the Calandbrug canal.

Graffiti covers the walls of a room where university students through the centuries have waited nervously to defend their theses.

A radio telescope for listening to the stars, based in one of the cloudiest countries in the world.