You stop midway between two worlds while an East German guard. his Russian-style carbine slung over his shoulder, ogles you through binoculars. Then your foot touches the accelerator, and you’ve left Checkpoint Charlie and West Berlin. The heavy, candy-striped steel crossbar goes up, and you show your passport at the gate. I had done this hundreds of times before, but this time was different. I wasn’t just crossing into East Berlin for the day. I was heading into what people in Bonn and West Berlin call “the Zone,” meaning the Soviet occupation zone of Germany, better known to most Americans as East Germany.