Letterboxing
Letterboxing is a kind of treasure hunt. Someone has hidden treasures in unsual places and you can find them with a compass and puzzles or clues from the internet.
See the website letterboxing-germany. There is an explanation of how to find these "letterboxes" or how to hide the own "letterbox". Moreover, you can find information how to start with this exciting and funny adventure. By the way, meanwhile, the most treasures (more than 60) are hidden in the Palatinate Forest.
Here you can download the puzzle which you will need to find our "letterbox" at Lindelbrunn close to Vorderweidenthal: Letterbox am Lindelbrunn