The denuded earthworks of a sub-square embanked enclosure, about 40-45m across, are set on ground sloping gently to the north, down to the wetland fringe of Cors Fochno or Borth Bog. Aerial photographs in drought conditions have revealed traces of an enclosing ditch with an intermittent bank and south-facing entrance gap.

The site was evaluated by the Dyfed Archaeological Trust as part of their Wetland Margins Survey of Cors Fochno (Poucher 2009), using geophysical and topographical survey together with an auger survey. The geophysical survey did not yield any further detail of the enclosure ditches beyond that known from aerial photography, but identified a low circular mound in the south-east corner and a series of other poorly-defined linear ditches and pits which are difficult to interpret. The gradiometer survey also identified possible traces of industrial activity beyond the enclosure to the east and south.

The lack of stone buildings, or indeed anything resembling the footings of a medieval chapel suggested in the place name, probably confirm an Iron Age or Romano-British date for this defended enclosure. Its sub-square form is more typical of the later prehistoric type of defended enclosure found in south Ceredigion. In north Ceredigion square or polygonal enclosures, perhaps denoting Roman influence, are more rare and include key sites like the trapezoidal enclosure below Penycastell, Llanilar (NPRN 400287) which lies in the neighbourhood of the Abermagwr Roman villa. It is probably significant that the square enclosure at Ynysycapel lies close to an area of Iron Age and Roman lead-smelting but its chronology and function could only be established through excavation.

Reference:
Poucher, P., 2009. Wetland Margins Survey: Cors Fochno. Dyfed Archaeological Trust report number 2008/114. Unpublished.

T. Driver, RCAHMW, 2012