Banc-y-Castell is a prominently sited hillfort dominating a projecting spur at the eastern end of the valley of the Melindwr. The defences around much of the univallate circuit are slight, enclosing the summit of the spur which measures about 150m east-west by 100m north-south. On the east side, crossing the neck of the promontory, are more complex gateway earthworks forming a `barbican'. The Cadw field monument warden notes that these gateway earthworks may have been disturbed by later activity such as quarrying or prospecting. Possibly also the site of a later castle described as Old Goginan or Nant yr Arian in 1216.

Source: Driver, T., 2005 The Hillforts of North Ceredigion: Architecture, Landscape Setting and Cultural Contexts. Unpublished PhD thesis, The University of Wales, Lampeter, Department of Archaeology and Anthropology.

RCAHMW, December 2008

'The earthworks at the east end of the hillfort are certainly odd, for they appear to run in an arc counter to the general curve of the hillfort defences around the edge of the hill. It seems that the isthmus linking the summit to the rest of the ridge has been scarped to form a tongue of raised ground running parallel to the approach road to the fort gate, with a shallow outer ditch. The earthwork does not appear sharply defined enough to be a medieval castle nor look convincing enough to be the result of later mining activities.'
Field notes written by Paul Davis after a site visit conducted on 23rd March 2019
RCAHMW, 3rd May 2019