Brief EH description:
Caer-Din Ring is sub-rectangular in plan. Its overall dimensions are approximately 114m east-west by 122m north-south, and its internal area is about 0.85ha. The earthworks which define the interior of the settlement consist of a bank, constructed of earth and stone, and an external ditch. The bank is between 6m and 9.5m wide, and stands up to 1.8m high. The width of the ditch is between 3m and 4.5m, and along part of the outer edge on the north western side its steep rock-cut face is still plainly visible. The original entranceway into the settlement is on the eastern side and is 4m wide. A smaller entranceway at the north west corner of the enclosure appears to be a later feature. Within the interior there are a series of level platforms, some of which are partially cut into the gently sloping ground. These platforms provided level areas for the construction of houses and ancillary buildings.
Much more here:
list.english-heritage.org.uk/resultsingle.aspx?uid=1021280&searchtype=mapsearch