That combination, a borough still functioning on paper long after its population had gone, gives the place its peculiar character. It was never walled, or at least no walls have been confirmed, though a possible fosse, a defensive ditch, hints at some attempt at fortification. What survives above ground is a cluster of roofless but substantial monuments standing in fields that remain in strictly private ownership.

Clonmines was founded by the Marshals, the great Anglo-Norman lords of Leinster, possibly as a sheltered alternative to their port of New Ross for ships unwilling to round Hook Head in bad weather. It was in existence by 1233, when a road to Wexford is mentioned, and in 1247 it passed to the Mortimer fief of Kildare as part of the division of the Leinster lordship, perhaps with the intention of serving that territory as a port. No founding charter is known. The Augustinian friary, suppressed in 1540, still had 11 named tenants in the town at the time of its closure. When the friary lost its function, the nearby silver mines at Barrystown, about 800 metres across the estuary, may have given the town a second life into the 17th century. Ultimately, though, what ended Clonmines was geography rather than violence: the gradual silting of the mouth of Bannow Bay cut off its overseas trade, and by the time Robert Leigh wrote about it in 1684 the town was empty. The Civil Survey of 1654 to 1656 had still recorded 15 proprietors in the parish, so the decline was relatively swift.

The surviving monuments include the parish church of St Nicholas, an Augustinian friary with its enclosure, two tower houses attributed respectively to the Sutton and FitzHenry families, a structure known locally as the Cowboy's Church which appears to have been a fortified church, and a standing gable from a 16th or 17th century house associated with the Purcells. There is also a trace of a roadway running south-west from the town. Because the site is in private ownership, access is not straightforward, but the ruins are visible and the layering of ecclesiastical, defensive, and domestic buildings within a single abandoned settlement makes Clonmines one of the more complete ghost towns of medieval Ireland.