This 47-story "M" needed 20 years to be completed

An industrial relic is now one of Europe's most staggering art spaces.

This magnificent market stands as a poignant symbol of the suffering caused by the Spanish Civil War.

An ancient octagonal weather station named for the eight Greek gods of wind.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

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

Vienna's giant wonder wheel had a starring role in one of the greatest noir movies of all time.

Op-art architecture designed for happiness.

One of the best collections of wax anatomical models in the world.

Built to give thanks for the passing of a plague epidemic, this cathedral is a one-of-a-kind architectural hybrid.

The final resting place for the remains of 143 Habsburg royalty.

A tropical paradise just a short trip from the opera house is filled with beautiful winged creatures.

This former insane asylum now holds a pathological anatomy museum.

Theme park featuring miniature replicas of European monuments.

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

Descend into the tunnels to experience the life of a coal miner.

A giant bug impaled on a 75-foot-tall needle.