That lopsided outline is not accidental; the wall was apparently bent and angled to work around the existing lands of the Franciscan and Dominican friaries, giving the whole defensive perimeter an unusually contorted geometry that still puzzles anyone trying to follow it on a map. At its most substantial, the limestone rubble wall once reached 6.4 metres high and 3 metres thick, built with dressed, mortar-bonded inner and outer faces packed with a core of small stones and mortar, and furnished with a pronounced sloping base known as a base-batter, which both stabilised the structure and made undermining it more difficult.

The town's formal civic identity began to take shape in the early thirteenth century, when Archbishop Donat O'Lonargan (1216 to 1223) elevated Cashel to borough status, granting burgage tenements to settlers and reserving a yearly rent of twelve pence per plot for the archbishopric. A burgage was a standard urban landholding of the medieval period, typically a long narrow plot fronting a street, held in exchange for fixed rent and certain civic obligations. Around fourteen years later, Archbishop Marianus O'Brien (1224 to 1238) issued a formal charter to the reeve and twelve burgesses. The physical wall was probably substantially in place before around 1265. Murage grants, which were tolls levied on goods entering a town and ringfenced for wall construction or repair, were awarded in 1303 for four years and again in 1319 for five. By 1378, Cashel was exempted from paying a similar toll at Clonmel, suggesting it was already collecting its own. Corporation records running from 1673 to 1773 name at least five gates, among them Canopy Gate to the east, variously called the Upper Gate and Dublin Gate, and the West Gate, also known as Lower Gate and St. Nicholas' Gate. In 1677, siege fortifications left over from an earlier conflict were declared dangerous obstructions at Canopy Gate, and a tower in the churchyard of St. John's was described as a "little tottering tower" ready to fall. By 1732, Lower Gate was taken down as a hazard, and by the late eighteenth century the Corporation itself acknowledged the walls and gates had long since fallen into decay.

Only ten fragmentary sections of the wall survive today, none of the five named gates among them. The best-preserved stretch runs along the southern sector, particularly at the south-west angle and eastward to St. John's Church of Ireland graveyard, whose boundary follows the line of the wall exactly. In the north-west sector, a well-preserved sally port, a small concealed gate built into the thickness of the wall for discreet passage in and out during a siege, survives largely intact. Its round-headed arched passage still shows the impressions of the plank and wicker shuttering used as temporary support when the arches were first set in lime mortar, a rare trace of the original building process preserved in stone.