Y Bwlwarcau is a enclosure complex, Iron Age or rather later, set on east-facing slopes on a broad spur of Mynydd Margam. It is a complex multiperiod site, but one coherent layout can be identified, as well as obviously later trackways and medieval type house platforms (NPRN 15248). The published inventory description can be ammended in the light of examination of RCAHMW air photo coverage.
The most obvious layout had a strongly defined inner enclosure set within a much larger outer enclosure and linked by an approach way. The 0.3ha inner enclosure is roughly pentagonal measuring some 64m across. It is defined by two to three lines of ramparts and ditches. The entrance faces east where its outer ramparts turn to form a funnelling approach way at the end of which they swing back to enclose the roughly concentric curvilinear 4.3ha outer enclosure. This rests on the steep slopes above Cwm Cerdin to the north and elsewhere it appears to have been defined by two widely spaced ramparts.
A small, generally rectangular enclosure lies between the inner and outer circuits to the south of the approach way and is attached to the ouer rampart. It is about 50m north-south by 38m and is defined by a rampart and a relatively broad ditch. This could be a contemporary feature rather than a later addition.
Other features could be earlier or later than the layout described above. A continuation of the outer rampart appears to run across the mouth of the funnelled approach way, where there is also a platform house. This could either be a later blocking or else the entrance was inserted into an already existing outer circuit. The outer circuit itself stands within a larger, irregular, comparatively weakly defined 7.4ha enclosure, which again might be earlier or later.
To the east of the enclosure complex are a further house platform (NPRN 307284) and a cairnfield (NPRN 307280), possibly an agricultural clearance feature.
Source: RCAHMW Glamorgan Inventory Volume I.2 Prehistoric & Roman (1974), 57-61, fig 33, No. 693
John Wiles 14.12.07