There are a couple places (private property) in the Texas hill country that will rent you an area for the day. You can dig and what you find is yours from what I've heard.

Its fun watching the kids eyes light up when they find one...or think they have found one. I'd love to find an old campsite. I've never found anything overly unique or valuable that I know of, other than time spent with my kids.

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Smells like victory...