One of the largest barracks of the Austro-Hungarian monarchy's military is now an abandoned ruin.

A Hungarian optometrist's charming collection of Asian art and curiosities.

This Hungarian stilt village is built in a lake that never freezes over due to the power plant that that uses it as a cooling pond.

The oldest private art gallery in all of Hungary.

Legions of Roman soldiers bathed in this ancient spa complex under a Budapest transit station.

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

A forgotten graveyard lost in the tangles of an overgrown garden.

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

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

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

A Trabant car, a kangaroo statue, and a plethora of plants take over this abandoned-factory-turned-bar.

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

The first island in the world designated a light-pollution-free astronomical observation point.

An 800-year-old island castle in Guernsey's main harbor.

Underground hospital complex constructed by slave laborers during the German occupation of the Channel Islands.

An intricately decorated tiny place of worship.

1% of Greenland's entire population used to live in this single building, which is now slated for demolition.

A stunning little chapel built on a rock in the Mediterranean Sea on the Greek island of Leros.

Once the largest rope factory in Greece, this abandoned plant now stands like a ghost of industry past.

The remains of a military communications outpost still stand on this Greek island.

This lesser-visited World Heritage site in Athens boasts an impressive ensemble of medieval gold mosaics.

The home of Greece’s national poet sits crumbling in the middle of a popular tourist district.

A unique housing complex born from the aftermath of the Greek Civil War.

On top of a hill, this Catholic church overlooks the most Catholic island in Greece.