If you have dowsed a signal, red X is probably what you were picking up on, about 23-25 feet in the direction of your red arrow. I think it is a very valuable artifact, rather than a buried treasure, but could be wrong. Red circle is for an artifact might be worth recovering, probably less than 6 feet away. If you are tunneling in, looks like you could be down a little far. Don't recommend digging into the roof of that tunnel, looks too dangerous for that type of recovery. Green circles for other archaeological signals.