This huge abandoned fortress hidden inside a mountain holds a world of subterranean secrets.

A Franco-era dam flooded (almost) everyone out of this centuries-old Aragonese town.

A stunning Art Nouveau cinema in the heart of Budapest.

On a teardrop-shaped island in the Danube, the ruins of a convent and the final resting place of a saint.

This small condiment museum makes all manner of mustards with a 200-year-old mill.

The statue of a legendary giant who carried Christ and shouldered the world's sins.