East German police on patrol boats tried to disrupt filming by shining searchlights at the cameras. Director Robert Siodmak assembled a decoy crew to distract the East Germans and filmed the scene along the canal a short distance away.
Based on the escape of 28 citizens of East Berlin who escaped by tunnel on 24 January 1962.
A duplicate Berlin Wall used for the film One, Two, Three (1961) was used in this picture. It was located only four blocks away from the real wall.
The tunnel was constructed with movable sections at Ufa Studios.