Beneath the floors of Waterford's public library on Lady Lane, the foundations of a medieval gate tower sit quietly preserved, invisible to anyone browsing the shelves above. That is perhaps the most telling detail about Waterford's town defences: much of this elaborate circuit of walls, gates, towers, and ditches that once enclosed one of Ireland's most significant medieval cities is still present, but hidden in plain sight, absorbed into buildings, buried under car parks, or glimpsed only as a stretch of weathered stonework at the back of a property.

The defences developed across several centuries, beginning earlier than the standing masonry might suggest. Excavations by A. Hayden during 1987 and 1988 at Bakehouse Lane uncovered an earthen bank and external ditch dating to the second quarter of the 12th century, the bank originally topped by a timber palisade and later revetted in stone. This earlier line of defence was already being superseded by the mid to late 12th century, by which point houses were being built outside it. The more substantial stone wall circuit came later. The section running from Reginald's Tower westward, some 400 metres of near-continuous wall, was built along the southern edge of the Viking town, reaching up to 4 metres in height externally and potentially concealing a considerable depth of archaeological deposits on the city side. St Martin's Gate, inserted into this wall early in the 13th century, comprised two D-shaped towers flanking a passage just 2.4 metres wide, protected by a portcullis. One of its towers was later rebuilt in the 18th century and the gatehouse absorbed into a large private house. On the western side of the city, Arundel Gatehouse, attested from 13th-century sources, served for a time as both a document store and later an arms depot before being demolished in 1696 to make way for a courthouse. The riverfront wall, running between Reginald's Tower and the long-vanished Turgesius' Tower, known only from 17th-century maps, once had five gates opening onto a wooden waterfront; by the 17th century those gates faced stone piers projecting into the Suir. A rectangular tower on this stretch, later called Keyser's Castle, stood where the city's post office now is.

The Beach Tower, on the western suburban circuit, is the most complete surviving fragment of the defences beyond Reginald's Tower itself. A two-storey rectangular structure possibly identifiable with the 'Baker's Tower' mentioned in a document of 1482, it sits on a cliff face that rises 14.7 metres at its highest point. Its interior retains a barrel-vaulted chamber, mural stairs rising through the wall thickness, a cross loop at the rounded northern angle, and an arrow loop on the first floor. The original entrance, now blocked, was set at second-floor level in the south-west wall, a deliberate choice that would have made uninvited access considerably more difficult.