What survives at Passage East on the Waterford estuary is easy to miss: a small, thickset fragment of masonry incorporated into a breakwater, its five gun loops still aimed at a river approach that has long since ceased to feel threatening. The corner tower that contains them is roughly three metres across and a little over three metres tall on the outside, a modest remnant of something that was once considerably more substantial. Its preservation is accidental, a byproduct of later harbour engineering rather than any deliberate act of conservation.

The story behind it reaches back at least to before 1568, when a large circular tower already stood here. In 1590, Edmund Yorke extended the fortification significantly, demolishing several existing houses in the process to make room for a mortared enclosure wall, probably with corner towers, and an internal earthen rampart. The resulting fort controlled river traffic at a strategically sensitive point on the approach to Waterford city. Waterford Corporation administered it until November 1649, when Cromwellian forces took it; over the following year, those forces successfully held off Confederate attempts to retake the position. The fort continued to be maintained through the rest of the seventeenth century, and in around 1685 Sir Thomas Phillips drew up plans for an ambitious star-shaped fort, the kind of geometrically precise artillery fortification that had become fashionable across Europe, on nearby Carrickcannuigh Hill. That project never left the drawing board. The existing fort was eventually abandoned in 1711, then briefly re-examined and reoccupied in the 1780s following a survey by Lieutenant General Vallancey, the military engineer and antiquarian. That renewed interest came to nothing lasting, and the remains were largely demolished in the late nineteenth century.

The surviving corner tower, its dimensions carefully recorded, sits within the fabric of the breakwater near the old blockhouse site. The gun loops, narrow splayed openings designed to allow a defender to fire outward while remaining largely protected, are the most legible feature remaining, and they give a concrete sense of what the original structure was built to do.