Bannow was once a functioning borough with named streets, burgage plots, a castle, a market cross, and a population that may have reached around 160 by 1307. Today, almost none of it is visible to the naked eye. What finished it off was not war or plague but geology: the gradual silting of Bannow Bay and its channels to the open sea slowly strangled the settlement's access to trade and water, leaving it to dwindle over centuries into cabins and rubble.

The area takes its significance partly from its proximity to Bannow Island, just across a channel to the west that has itself silted up since the mid-seventeenth century. That island was the site of the first Anglo-Norman landing in Ireland. The town that grew on the adjacent peninsula did so under Anglo-Norman lordship: the territory of Bargy had been granted to Hervey de Montmorency, who in turn granted the church of Bannow to Christchurch in Canterbury, which later passed it to Tintern Abbey. By the time of the Dissolution of the Monasteries in 1540, some 120 acres of Bannow village were among Tintern's recorded possessions. The town itself was probably never fortified, having no royal charter, though burgess rights, the standard commercial privileges of a medieval borough, were extended to its inhabitants. A survey recorded in the Book of Survey and Distribution in 1655 still lists six named streets, High Street, Lackey Street, New Street, Lady Street, Weaver Street, and Little Street, along with a castle, six thatched houses, sixteen house plots, and twenty-five garden plots. Writing in 1684, a commentator named Leigh described only ruins and a few cabins. Yet even in this diminished state, Bannow continued to return two members to the Irish Parliament until the Act of Union in 1800.

What remains visible above ground amounts to the shell of St. Mary's church, the site of a castle nearby, and the location of Lady's Well. Beneath the fields, aerial surveys carried out by Simon Dowling in 2017 and 2018 have captured cropmarks revealing the ghost outlines of New Street and Little Street as parallel banks running eastward from the shore for roughly 120 metres. A tidal mill first mentioned in 1307, described as ruinous by 1324, has been more recently identified from a surviving causeway dam across a small inlet just north of the nearby Brandane church site. Lady Street, the easternmost of the town's thoroughfares, once continued beyond Lady's Well and reached the coast about 1.8 kilometres to the east; that stretch has since been entirely eroded by the sea, its continuation surviving only as a dead-end road at Cullenstown several kilometres further on.