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

Long-abandoned art nouveau baths beneath Milan's Piazza Oberdan.

Stuck in the middle of a modern Madrid city block are the remains of a 19th century sports complex.

The earliest known map to show America, discovered by accident at a Paris bookshop.

Over two centuries old and counting, Madrid's massive botanical garden contains one of Europe's only desert environments.

Abandoned for decades, trains still pass through the now-restored remains of one of Madrid's first metro stations.

Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.

An ancient Egyptian temple in the middle of Madrid, Spain.

This hidden art nouveau gem was designed by an architect in search of a national style.

Sitting beneath an unremarkable residential building is a museum devoted to classic Pinball.

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

From Austrians to Nazis to Soviets, this historic Budapest fortress has a history as complex as the city itself.

Museum dedicated to the terror regimes of Hungary.

This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.

This Budapest bar allows drinkers to leave their mark on the walls, floor, and even ceiling.

The world's largest wooden structure.

Together they left this world, and together they shall remain for all eternity.

What was once a bustling mining installation is now a bustling hub of contemporary art.

The "stairway to heaven" lookout tower was built to resist weather, arson, and the laws of physics.

A once-magnificent collegiate church is falling into ruin.

This sprawling Belgian fort was once thought of as impenetrable but now it is simply an abandoned relic.

This abandoned Belgian fortress is purposefully being left to nature.

Hiding the longest subterranean river known in the world.

A Belgian self-built tower inspired by the Bible and ancient civilizations.