In the pedestrian zone in front of the coffee bar, a man had set up a chessboard. When he saw my curious and astonished look, he invited me to play a game. But I play pretty well, I said, and he replied that at least he would learn something. He was new in town and wanted to finish his doctorate in mathematics here. I asked what the topic was. I can no longer reproduce his answer even now, a few hours after our chess game. Something about geometric symmetries in higher-dimensional space. He explained it to me, and it could just as well have been a fairy tale as a scientific topic. When something is beyond our imagination, it is a miracle and reality at the same time.