The phrase 'the walled city of Cork' conjures up the familiar picture of the old city centre of Cork between the North Gate and South Gate bridges surrounded by a permanent, unbroken wall. The actual history of the building of the walls is more complicated than this. The south island, the area known in medieval times as the civitas, was the first section of the city to be fortified by the Normans. Archaeologists think that the south island was enclosed by the early thirteenth century. The wall around the south island was composed mainly of limestone. The north island, Dungarvan, was not entirely enclosed until the late thirteenth or early fourteenth century. The wall around the north island was composed mainly of sandstone.
The technical difficulties of building a wall around islands in a tidal estuary were considerable and the maintenance of the walls caused considerable expense. The strata on which the walls were built were prone to subsidence and the constant ebb and flow of the tide also undermined the integrity of the structure. On the difficulty of maintaining the walls, the City Archaeologist, Maurice Hurley has written, 'The unified circuit also belies the vulnerability of a stone wall built on a marsh, constantly assailed by tide and riverine floods, where private interests maintained personal doorways and where public authorities frequently provided no more than an outward appearance of consistency and strength.' Finance to maintain the walls was raised by grants and taxes known as murage grants and murage taxes. Major repair work on the walls took place on a number of occasions. The final extensive rebuilding project on the walls took place in the early seventeenth century. A section of the city wall is visible in present-day Bishop Lucey Park.
The walls were built mainly on a gravel bed and tapered upwards from a broad base, a feature technically known as a batter. The stones between the inner and outer faces of the walls consisted of rubble mixed with mortar. There were fortified gates at the locations of the present-day North Gate and South gate bridges. A water gate was located near present-day Hanover Street. A Marine Gate, allowing access to ships, was on the eastern side of Castle Street. Fortifications on each side of this gate are often thought to be the castles depicted on the coat of arms of Cork city but modern historians think this is not the case. There were up to 16 defensive towers along the city walls. The exact height of the wall is now uncertain. Estimates vary from about 3 metres to 6 metres. The walls enclosed an area measuring approximately 645 metres north-south and 225 metres east-west, enclosing an area of approximately 14.5 hectares.
The purpose of the walls was, of course, defensive. Cork could have been regarded as a Norman frontier town surrounded by a potentially, and often actually, hostile native population. With the advent of artillery, town walls became redundant as defensive structures. The siege of Cork by Marlborough in 1690, when extensive use was made of artillery, effectively spelt the end of the defensive role of the walls of Cork. They were allowed to fall into disrepair and sections of them were demolished. Houses were built using the remains of the town walls as foundations - a humble, but practical, use for the once proud walls of Cork.