Somewhere beneath its streets and river margins lies the borough of Duiske, a functioning Anglo-Norman town complete with a mayor, burgesses, a justiciar's court, and a market, yet its precise layout remains unknown. The Down Survey maps of 1655 to 1656 record only an abbey, a castle, a mill, and a weir, with no town shown at all. Whatever urban fabric had existed by then had either collapsed or become too unremarkable to draw.

The Cistercian abbey of Duiske, founded in 1204 by William Marshall, Earl of Pembroke and Leinster, with a formal foundation charter following in 1207, clearly generated a settlement in its shadow. A grant dating to around 1255 refers to 'Baliodowisky', interpreted as meaning the town of the black water, from the Irish dubh-uisce, a reference to the Douske River that still runs through the town today. By around 1261, Latin charters were recording a 'Noue Ville iuxta Baruwe', a new town beside the Barrow, and by around 1280 there were multiple leases of burgages, the standard plots of land granted to residents of a medieval borough, transacted between named individuals and the abbey. One lease from this period is witnessed by a man identified as 'Elya preposito Noue Ville', Elias, mayor of Newtown, while another is witnessed by named burgesses of the settlement. The justiciar's court sat there in 1305 and again in 1314, with Edmund le Botiller presiding. In 1618, Edward Butler of Low Grange was granted a patent for a Thursday market and two annual fairs, on 11 June and 28 October, suggesting the town retained some commercial function into the early seventeenth century.

The current layout of the town offers a few quiet clues to what came before. The High Street, running east to west to the west of the abbey on the first edition Ordnance Survey map of 1839, is thought to preserve the line of the medieval town's principal thoroughfare. The Main Street running north from the bridge appears to be a later addition, its southern end apparently cutting through monastic remains that post-date the dissolution of the monastery in 1540. The Douske River, which divides the town, may itself mark the western boundary of the old monastic precinct, with the medieval borough having grown up on the far bank.