Something interesting but probably unrealistic: We know there was a clue box at the Hohenzollern bridge in Cologne which has locks all around it, and there is also a bridge in Ljubljana which also happens to have locks on it. It would be cool if there was some type of task connecting the two bridges. Even if it's something minor like receiving a key in Cologne to use in Ljubljana, or it could be a real task where they need to remember some part of the bridge in Cologne to help them find a clue in Ljubljana