Totally agree. LIDAR would be great over the plantation (don't know if English Heritage have the area targetted) to show up target areas. The marks on the rock outcrop side are really impressive but look like none I've seen on-line or in books. The large whole could be formed by natural processes I guess (rocks in the bottom of a stream bed) but the other feature is a grove with a "bridge" over the top, ie a "tunnel" under the rock. This is in soft "limestone" like (I'm no geologistc) rock.

The whole planation is very tightly planned so it would be hard to find anything on foot.

Mac