On the Spree bank, discover one of the last reminders of a symbolic wall that divided, and was torn down by the people.

Infamous and now demolished panopticon prison built by its former inhabitants.

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

The celebrated eyesore created by starry-eyed sweethearts.

The world's first electric battery-powered submarine.

A former steam-powered mill from the 1800s is now an industrial park with a giant steel dragon slide.

Baroque celebration of the end of the Great Plague of Vienna.

A 12th century church completely covered in shells.

Hundreds of caves once used to store grains and animal feed.

Devastated landscape used for hundreds of years by the Romans as their primary mining site.

Danish tourist destination well known for open stalls where vendors sell marijuana on the street.

The earliest known map to show America, discovered by accident at a Paris bookshop.

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

Stone Age solar temple is aligned with the sun on each equinox and solstice.

A huge cathedral single-handedly constructed by one eccentric monk.

Op-art architecture designed for happiness.

A spherical "micro-nation" in the heart of Vienna.

Commonly acknowledged as the only public monument to the Devil himself.

The old observatory in Copenhagen has a spiral corridor used as a racetrack.

The world's most elegant power lines.

An ancient Egyptian temple in the middle of Madrid, Spain.