The largest free-standing aquarium in the world resides in a hotel lobby in Berlin.

A tour of underground Berlin takes you through WWII air raid shelters and tunnels used to smuggle people out of East Germany.

An eerie, derelict amusement park in Berlin.

One of Europe's oldest libraries.

Ancient Egyptian wigs, South American feather headdresses, a bounty of anthropological artifacts in Oxford.

A hidden bathhouse in one of Stockholm's oldest and busiest neighborhoods is open to anyone who can find it.

Sweden's first nuclear reactor, R1, can be visited 25 meters underground.

The natural history museum displaying the British bird collections and dioramas of Edward Booth, free of charge.

This tunnel entrance is built to resemble a grand castle but no one is quite sure why.

An ultra-modern diversity park in Denmark has turned an entire city block electric pink.

London's creepiest cemetery was once the site of dueling magicians and mobs of stake-carrying vampire hunters.

Oxford University's stateliest library seems designed to make students truly feel the weight of knowledge.

The names Lúthien and Beren can be found inscribed on the shared grave of the famous writer and his beloved wife and muse.