The monument comprises a fort of prehistoric date, visible as upstanding stone walls and earthworks. The monument was first scheduled in 1953. It is being rescheduled to extend protection to cover the whole of the archaeologically sensitive area. Forts of this type are characteristic of the late Bronze Age and Iron Age (first millennium BC).
The monument is situated within moorland on the summit of Barmekin Hill at about 275m OD. The monument comprises a multi-vallate hillfort (a fort with multiple ramparts and ditches), and is unusual in that it has five entrances. The fort is composed of five roughly concentric ramparts, with at least two phases of rampart construction visible. The earliest works comprise the outermost ramparts (from the outside, ramparts A, B and C). These consist of heather-covered rubble and earthen banks, which stand to a maximum height of around 2.8m, and enclose an area c.150m N to S by c.135m E to W. The second innermost rampart (D) is situated immediately inside these works and comprises a dry-stone wall surrounded by fallen stones. Both wall faces can be seen intermittently and reveal an original wall thickness of c.2.6m. The innermost enclosure (E) is also of dry-stone construction, and encloses an area c.115m N to S by 110m E to W. It is in a more ruinous condition than its neighbour, but is likely originally to have been more substantial, being approximately 3.7m in thickness and surrounded by a greater quantity of tumbled stones. In the SE, two heather-covered stone walls, 0.5m high, adjoin the walls forming the two innermost ramparts (D and E).
The fort defences are pierced by five entrances located on the NNE (entrance no. 1), E (2), S (3), SW (4) and WSW (5) sides of the fort. Of these, entrances 3 and 5 are blocked by the stone walls D and E, indicating that these walls were constructed later than ramparts A, B and C. With the exception of entrance 1, there are hollow ways associated with all of the entrances (sunken ways flanked by earthen banks). These emanate from the outer ramparts (A, B and C) to wall E, suggesting that the original fort comprised five ramparts, and that the stone walls (D and E) were built later, and on top of, the inner two ramparts. The latter were probably of the same rubble and earthen construction as ramparts A, B and C. All entrances are stepped to form a zig-zag, with the ramparts bending slightly in at each side of the entrance, except entrance 2 which is probably the fairly modern access way to the now ruined observatory, present within the interior.
At entrance 4, the gap through wall D is probably modern as access to it is barred by a line of upright stones on the W side of the hollow way. As there is an original entrance through wall E at this spot, and as wall E is more ruinous than wall D, it seems likely that wall D was constructed after E, blocking this means of access.
A ring-ditch house of prehistoric date, around 12m in diameter, has been identified some 14m W of the outermost rampart, immediately N of entrance 5.
The area proposed for scheduling comprises the remains described and an area around them within which related material may be expected to survive. It is almost circular in shape, measuring 232m N-S and 245m E-W (to include the remains of the ring-ditch house), as marked in red on the accompanying map.