The springer stones are the lowest wedge-shaped blocks of a vault, the point at which the curving arch begins its rise from a vertical wall, and here they remain, undisturbed, as the city above them was built up, rebuilt, and built up again across the centuries. It is the kind of detail that makes urban archaeology quietly disorienting: a medieval domestic space sealed beneath a street, still holding its shape.

The remains were uncovered during an excavation carried out by archaeologist Celie O'Rahilly under licence No. 95E120, when three test-cuttings were dug along Creagh Lane in advance of a proposed development. The second cutting, on the plot for No. 21 and running north-east by south-west, produced the most significant results. The inside face of the stone wall reached a total recorded height of 2.7 metres, incorporating the springer block and a further half-metre of wall above it. Fragments of the voussoirs, the individual wedge-shaped stones that form the body of an arch, were also visible at the south-western end of the cut. The crown of the vault itself would have sat beneath what was then a vacant site at No. 20. Near the base of the wall, excavators identified what may have been the clay floor of the cellar, with darker layered deposits beneath it sitting over natural sandy silt. The total depth reached 3.1 metres, though loose overlying fill made it difficult to record precise levels throughout. A third cutting, closer to the street frontage along the same wall line, revealed a brick cellar beneath No. 21 Mary Street, a later addition to the same structural sequence.

The site sits in the older part of Limerick city, in an area with a long record of medieval occupation. Nothing survives above ground, and access to the western half of the site was restricted during the original investigation, meaning the full extent of the building was never established. For anyone walking Mary Street or Creagh Lane today, there is little to indicate what lies below. The excavation record, available through excavations.ie, remains the most detailed account of what was found, and is worth reading alongside any visit to the area, if only to recalibrate how much of a medieval city can persist, unannounced, just out of sight.