Former hunting lodge of a duke who was an avid collector of impressionist works.

This former “ante-chamber to the guillotine” has been refurbished to illustrate the brutal history of French justice.

The history of radiation is on safe display at the foot of a radiation science laboratory.

The vast, legendary catacombs hold secrets much stranger than stacked bones.

Paris' linguistic guide to the international language of, yes, love.

This modest marker near Notre Dame identifies the very center of Paris.

The oldest stone house in Paris was built by its most famous alchemist.

Christ's blood allegedly preserved in a Belgian town.

Climb inside an iron crystal magnified 165 billion times its normal size.

A miniature city, once ruled by the Queen of the Netherlands.

A floating cat sanctuary on an Amsterdam canal.

There has been an astronomical clock on this spot since the 14th century.

The birthplace of Karl Marx is now a museum dedicated to the communist revolutionary's life and work.

The last bastion of Roman presence north of the Alps looms over a German town.

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

Visitors dating back to the 1600s carved their marks in the stones of the iconic tower.

The medieval network of canals hidden underneath the city is opened to explorers each year.

Walk in the footsteps of the gods and straddle two tectonic plates.

The former Nazi Germany concentration camp stands as a museum to remember this dark chapter in European history.

Archduke Ferdinand II's collection of rare objects is considered one of the oldest museums in the world.

The beautiful, ornate weather station is the most popular geocache in Salzburg.

This magnificent museum claims to house the cranium of a disciple and the skull of a pope.

King Ludwig I's collection of beautiful women.

This splendid tomb may look fantastic, but there's nothing in it...