He didn't understand me. I want to copy the dolmen (without its properties) and change the appearance of this copy to look like a dolmen.
For example, the Crystal of Knowledge. We copy it and change its appearance. (as a side effect, it gives +1 to knowledge, etc.). Moreover, we can take away this knowledge from heroes, and this procedure is less harmful for the hero than the procedure of taking away experience.
Or we can find another object that is more suitable.