In 2010 my extended family of about 60 people—spanning 4 generations—came together for a reunion. The previous year everyone had participated in a photo scavenger hunt (in addition to other activities). For this reunion, my wife and I offered to put on a treasure hunt for the family (which many did not know about).
This site describes the puzzles themselves (with solutions), an analysis of how the game turned out, and some behind-the-scenes information on what it took to design, put together, and run the hunt.