When my family moved to a new house when I was 13, I found a velvet ring box in the garden that had a sorority pin and a pair of dangly cameo earrings in it. That's the closest I've ever come to finding treasure. I still have the earrings, but I lost the pin.
I made a treasure chest for the kids I babysat and their dad took it to a small island near by and buried it. Then we made an old looking map for them to go on a treasure hunt with. They were the happiest kids you've ever seen!