When looking for the RSC at North Keig most people will park at the quarry. Walk down thru the trees and the famous circle is reached. For the fort, Neolithic, walk the opposite direction up the Hill Of Airlie. A walk of about a 1/2 mile. There is a path of sorts.
There are two walls one almost gone and the outer wall. In parts this stone wall is almost 8 meters wide and 1 meter tall. Some stones poke thru the turf. In the south eastern corner a 4 meter gap indicates the entrance. What a place for a fort. Magnificient views down the the Don valley, west to Strathdon, east to Bennachie and north looking towards the Brindy hill and road. (The road to Premnay.)
Also there is the remains of a cairn in the forts middle. The only thing left of the interior.
What is left of the cairn sits in the middle of the Barmkyn Fort, the only feature in the interior. Only a few scattered stones remain of the 8 meters wide site. A climbers cairn has been built on top. When the vegetation returns it will be very difficult to spot.