Castle Bank may have formed a large north bailey. The outline of a building in this area is likely to be the oak hall recorded at Cefnllys in the 15th century. A stone curtain wall and rampart extended along most of the hilltop rim. St Michael's Church sits at the foot of the hill next to the Ithon, to the west. Earthworks surrounding the church are commonly supposed to be the remains of the medieval town. Alternatively, several historians infer that the primary settlement may have been sited within the enclosure of Castle Bank, adjacent to the castles. During the borough's later history, the population may have been dispersed along the valley, instead of being focused in a nucleated settlement. The Norman motte-and-bailey castle was located on the bank of the Ithon further upstream, north of Castle Bank. History No archaeological excavation has been undertaken at Cefnllysmodern understanding of the site's history rests on contemporary texts. Prior to the 14th century, sources are limited to accounts of military campaigns and the castles are referenced in the Welsh chronicles Brut y Tywysogion and Annales Cambriae. Greater stability following Edward I's conquest of Wales resulted in a growth of documentary evidence in the Welsh Marches, though at Cefnllys this is largely restricted to rudimentary public records as the majority of the Mortimer estate archives have been lost. An extensive topographical survey combined with photogrammetry was carried out at Castle Bank in 1985 by the Royal Commission on the Ancient and Historical Monuments of Wales (RCAHMW), with a follow-up appraisal in 2006. Hillfort origins A number of scholars have suggested that the medieval castles utilised the remains of an Iron Age hillfort. Indications of a pre-Roman provenance include the ridge's large, elongated enclosure of , interpretation of visible earthworks and the extensive use of scarping and ditching to artificially steepen the gradient of slopes surrounding the hilltop. The archaeologist A. E. Brown tentatively linked the entrance hollow-way with this period, and the banks encircling the hilltop could also have an Iron Age origin. Other features previously posited as pre-Roman were determined to be medieval by the 2006 RCAHMW report, although it did not rule out the possibility of a hillfort. The complexity of earthworks on Castle Bank is compounded by alterations caused by later agricultural use and quarrying, making confident assessment difficult. Among recent archaeological studies, Chris Martin & Robert Silvester(2011) state that