Located on a west-facing slope the ridge of Bwlch y Garn is a house platform. The grassy terrace measures 17.5m long east by west, with split levels at 5m (0.4m step-down) and 10.8m (0.3m) from the upper end, though the latter 'step' may have resulted from disturbance. The platform is cut back into rising ground to form a hood 2m deep below the crest of a semi-circular stony bank capping the hood. This bank, to deflect water flowing off higher ground, averages 0.75m wide and is 0.2m - 0.9m high. The terrace is 5.4m wide at the upper end and 5.9m wide at the outer end where it is built out to 0.6m high.
The outer end of the terrace is marked by a stony spread. Below it are two small cairns of small stones:
SO17670976, 5m across and 0.2m high;
SO17670974, 3m across and 0.2m high.
Projecting from each long side of the terrace is a linear bank which crosses the lower arms of the hood, and is possibly one element of a later field system superimposed on the platform. To the north-east of the platform is a triangular enclosure measuring some 130m (north-east by south-west) by 90m, with a subdivision in its south-west corner just above the platform, containing an arcuate stone pile against the dividing bank. The enclosure is defined by stony banks up to 2m across and within it are cultivation ridges averaging 1m wide and 0.1m-0.2m high. These are on two alignments; north-east by south-west; and within the subdivision north-north-east by south-south-east. Ridges extend beyond the south-east boundary (air photos) suggesting that they may be not be directly related to the enclosure. Quarry spoil tips lie to the immediate south-east, and a later stone walled enclosure to the south. Further cultivation ridges are visible to the north, on various alignments, as far as about SO17651005 (air photos).
Sources:
GGAT, South-east Wales Industrial Landscapes (unpublished report).
NAW air photos (2013 coverage).

David Leighton, RCAHMW, 11 May 2016