Engineering the Berlin Tunnel

Fifty years ago, the CIA embarked on a project to intercept Soviet and East German messages transmitted via underground cable. Intelligence was collected to determine the best place to hit the target, and then concrete planning for a new collection site was begun.

The tunnel was 1,476 feet in length and consumed 125 tons of steel liner plate and 1,000 cubic yards of grout . . . This was not a small operation!