Not quite. Alpha is at the edge of West Germany, once past Alpha you are on an Autobahn (a highway) to Berlin and physically in East Germany but the Soviets hav

Not quite. Alpha is at the edge of West Germany, once past Alpha you are on an Autobahn (a highway) to Berlin and physically in East Germany but the Soviets have agreed that they won't do anything so long as you never stop until you reach Bravo at the border between East Germany and West Berlin. The route between Bravo and Charlie is inside West Berlin. Charlie's significance is that the Soviets will not (by the time Charlie is created) allow non-Germans to enter East Germany legally except via this point. The West has argued that this isn't what they agreed, but have eventually relented because it's apparent that arguing isn't helping.