But a LiDAR survey, which uses laser pulses to detect subtle variations in ground level invisible to the naked eye, has revealed something quite different beneath the grass: the ghost of a medieval town. Running north to south through what is now Dukesmeadows, a hollow-way, a sunken lane worn down by centuries of foot and cart traffic, traces the former spine of Flemingstown, a self-contained suburb that once housed a community of Flemish immigrants who had settled just outside the castle walls.

According to historians Hogan and Egan, Flemingstown was established as a dedicated settlement for Flemish colonists, tradespeople of the kind described around 1625 by the bishop and scholar David Rothe as fullers, bakers, brewers, and workers in linen and wool. Rothe wrote of paved streets, property plots, and a marble gate that stood on rising ground opposite three water mills belonging to the lord of the castle. The earliest surviving documentary reference to the settlement is a property grant of 1339, recorded as a messuage in the 'Villa Flemang', with further grants following in 1350 and 1366. An early fifteenth-century extent in the Ormonde Deeds puts the area of 'Flemyngeston' at eleven acres. By around 1413, however, it had been largely emptied, with residents transplanted to the manor of Danesfort, some three miles from Kilkenny, reportedly on the orders of the earl of Ormonde. The marble gate itself was eventually dismantled and its stone reused for another gate near the River Nore, somewhere between Green's Bridge and St John's Bridge. That second gate is gone too: it does not appear on the first edition town plan of 1840 and nothing of it remains today. The name lingered in civic records, appearing as 'Flemyn's-street' as late as 1448, and 'Ffleming streete' still features twice in the Civil Survey of 1654.

The hollow-way identified by the LiDAR survey runs through a large L-shaped enclosure roughly 200 metres north to south and 210 metres east to west, which may represent the remains of an enclosing rampart around the settlement, though a post-medieval landscaping origin cannot be ruled out. What appear to be burgage plots, the long narrow property strips typical of medieval planned towns, extend westward off the lane. The suburb probably stretched northward to give access to the Castle Mill, and the hollow-way is very likely the same route described in a 1628 document as 'Mill Street'. A road realignment along the former Archers Street, carried out around the year 2000, is thought to have cut through the southern part of the suburb without any archaeological investigation taking place beforehand.