At its peak, the Berlin Wall was 100 miles long. Today only about a mile is left standing.

Compared with other famous walls in history, this wall had a pretty short life span.

The Great Wall of China has been around for 2500 years. So have the walls of ancient Babylon—although its most famous part, the Ishtar Gate, is actually in a museum in Berlin.

But even though the wall dividing Berlin into East and West was only up for 30 years, it had a huge impact on the psyche of the city. It broke families in two. In the decade that followed, more than 2 million people fled from east to west. East Germany was losing its most skilled workers as they sought jobs--and to reunite with their families--across the border. And East Germany was losing face with every East Berliner who chose to defect.

And that’s why, in 1961, East Germany closed its border to West Berlin with a wall. But this isn’t a story about the design of the Berlin Wall. This is a story about one design to get through it—or really, underneath it. Ralph Kabisch, then a 20-something-year-old university student, was there.