The forbidden island of the Tuscan Archipelago may still contain buried treasure.

The largest underground lake in Europe.

A crumbling island fortress that seems to be covered in a field of stone crosses but is simply incomplete.

This historic island prison holds one of the dungeons from the Count of Monte Cristo even though it is a work of fiction.

Hiding the longest subterranean river known in the world.

Incredible labyrinth of man made caves.

This 19th-century zoological collection has withstood the test of time.

This towering church is home to a world-famous organ and a treasure trove of medieval art.

At this barrel organ museum, history and live concert keep Dutch street organ culture alive.

Oldest Museum of the Netherlands is a true cabinet of curiosities.

An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.

The cave of a 12th-century hermit is still visited and venerated today.

This noble mash-up in eastern Luxembourg is part Medieval, part Renaissance, all castle.

For a few short weeks in spring, this hiking path becomes a daffodil paradise.

Luxembourg's first beer museum honors the Grand Duchy's contributions to the art and science of beer-production.

Once the local rulers had gone these enchanting ruins housed common folk in an almost real life fairy tale.

A 12th-century castle featuring a sensory path where partially-sighted visitors can experience regional history through touch and sound.

This Luxembourg cave is covered in cryptic looking marks left by mining activity.

In the heart of Luxembourg's "little Switzerland" weaves a breathtaking natural sandstone canyon with a mythological past.

This small gallery nestled inside an old botanical glasshouse is a quiet place to enjoy art and nature.