Lets look at this and think about a few things. 1. It could be a well but there are a couple of things that are not characteristic of wells. Wells aren't tapered as they go down. Remember someone had to dig this by hand . If it is a well and they took the trouble to stack these rocks inside it, why didn't they use mortar to hold them in place? 2. Why would you dig a well so close to a stream when you could just use water from the stream? Afterall , it appears to be the same depth as the stream right? If the stream is dry then so is the well. ..this is treasurenet so lets consider its use in a treasure meaning. What if someone buried something valuable about 5-10 feet from a stream intentionally. What if this was built so that it would be difficult to retrieve the contents? If you started at the top and worked your way down you would've had to remove every stone one by one as you worked your way down(considering that at the time this was constructed it wasn't open on the side the way it is now because time and erosion has washed out half of it). So, you have his hole filled full with stones next to a stream,. with something valuable in it. If you tunneled in from the side of the stream(remember, at the time it was constructed it was farther from the stream) and stacked the stones carefully horizontally so that if someone tried to pull them out from the side then it would create a trap because the stones that are stacked vertically would have collapsed. Therefore, this could be a carefully constructed treasure pit...ok, maybe not. Maybe some bored kids were playing with rocks a hundred years ago. Lol