I was wandering around the industrial ruins of as-yet-unfinished Lehrter Bahnhof -- what will one day be Berlin's most massive and dazzling transit hub -- when I came across this sign. What does it mean? It's just a man inside a circle! It could mean anything! Does it mean you're not allowed to go past the metal gate? Or that you are? I stood there for about five minutes, confused, just staring at it.