Letterboxing is an old treasure hunt game. The general idea is to obtain a small ink stamp (traditionally this is carved to be unique) and to follow clues to find small hidden caches with notepaper and inkpads for you to leave your mark in. Some clues are very easy to follow... fun for kids (accompanied by adults). Others are rather more difficult to decipher. There are several letterboxes in Davis... go to http://www.letterboxing.org and search through the California entries for Davis.
The newfangled version of this pastime is Geocaching.
