Somewhere beneath Catherine Street in Waterford, between a courthouse and a hall built partly from the rubble of what it replaced, lies what remains of a medieval Augustinian priory. Not ruins in the conventional sense, not a shell of arched windows or a fragment of cloister wall, but an absence: a site so thoroughly absorbed by later construction that its last physical traces were carted away in the mid-nineteenth century to make way for the Waterford Protestant Hall. The priory of St Catherine survives now mainly as a problem of historical cartography and a question of where, exactly, the ground beneath Catherine Street was once sacred.

The priory was founded before 1200, with King John later claimed as its original patron, though building work was apparently still under way as late as 1290, suggesting a long and probably piecemeal construction history. The Augustinian canons, a religious order following the Rule of St Augustine and living a communal life of prayer and pastoral work, maintained the site for more than three centuries. It was suppressed in 1540 during the dissolution of the monasteries under Henry VIII, at which point the church was still standing. A map dated 1590 shows four roofed ranges of buildings within what had by then become a star-shaped fortification, meaning the priory structures were pressed into military use even after the religious community had gone. The ruins continued to appear on Phillips' map of 1685 and on a late seventeenth-century map later published by Ryland in 1824. By the time the Protestant Hall was being built in the 1850s, only the last remnants survived, and those were cleared during construction. A grave discovered on site at that time contained an ecclesiastic, buried with a bronze signet ring, a small detail that connects an otherwise vanished community to a specific, nameable individual. Archaeological testing carried out around 2008 in the Bolton Street Yard, roughly fifty to a hundred metres north-northeast of the courthouse, found deep river silts well below the modern street level, overlaid by later industrial debris, but no trace of St Catherine's itself.