Close to the entry to the Plotting Room are the quite well preserved remains of a small Engine Room. This provided power to the Plotting Room and the Battery Observation Post on Mount Serapong. Remains of some cabling are still to be found where it passes through the old 9·2 Inch Shell Store.
As can be seen, the Plotting Room is not a safe place to visit. During the 2006 archaeological survey, some period monopoly pieces were found, and a 1941 coin.