Running through it is a hollow-way, the sunken trace of an old routeway, and on its western side are what appear to be burgage plots, the long narrow property strips typical of medieval urban settlement. None of this is visible in any dramatic sense; it took a LiDAR aerial survey in 2010 to bring the features into focus. What those low earthworks most likely represent is the ghost of a vanished suburb called Flemingstown, a self-contained colonial quarter that once sat just outside the castle walls and housed, according to tradition, a community of Flemish craftspeople.

The origins of Flemingstown are described by the 19th-century historians John Hogan and John Egan as a planned settlement for Flemish colonists placed deliberately to the east of the castle. The earliest documentary evidence, however, is a 1339 grant of a messuage in the 'Villa Flemang', with further property grants recorded in 1350 and 1366. An early 15th-century extent in the Ormonde Deeds puts the 'Flemyngeston' at 11 acres. Writing around 1625, the Catholic bishop David Rothe gave a vivid account of the suburb as it had been: paved streets, fortified dwellings, burgage plots, and a marble gate facing the castle's water mills on the far side. He described its founders as fullers, bakers, brewers, and workers in linen and woollen manufacture, a third wave of settlers arriving after the Irish and English had already established themselves. By Rothe's time the place was already empty. Around 1413, according to the antiquary John Prim, the earl of Ormonde had moved its remaining inhabitants to the manor of Danesfort, three miles outside Kilkenny, to work as agricultural labourers. The marble gate itself was eventually dismantled and its stone reused for a riverside gate on the Nore, somewhere between Green's Bridge and St John's Bridge. That gate too has since disappeared, not appearing on a town plan of 1840 and leaving no trace today. By 1663, when Sir William Flower wrote to the duchess of Ormond about twelve acres of former burgage land east of the castle, the suburb had long since been absorbed into demesne parkland. It was that process of enclosure and landscaping that preserved the earthworks, even as it erased almost everything else.

The enclosure sits within what is now Castle Park, and the LiDAR-identified earthworks are subtle enough that they would be easy to walk over without noticing anything at all. The hollow-way and the faint ridge-lines of former property plots are the closest thing remaining to a street plan of Flemingstown. A road realignment on the Bennetsbridge road around the year 2000 is thought to have cut through the suburb's southern extent without any archaeological investigation taking place, so what survives in the parkland may be the most intact portion of a settlement that was, even by the early 17th century, already being described in the past tense.