What makes the site at 48–50 Mary Street particularly curious is not just the age of what was found, but the sheer layering of it: medieval dump deposits, a burgage plot boundary marked by timber stakes, wattle-covered drains, a fragment of human skull, and mortar bomb fragments, all compressed into a plot along what was once the medieval city's principal street.

The excavations were carried out by archaeologist Tracy Collins of Aegis Archaeology Ltd., with work undertaken first in 2000 under licence 00E0635, and extended in 2002. The city archaeologist at the time, Celie O Rahilly, formulated the trenching brief and monitored the initial overburden removal, a precaution prompted by the known extent of later cellaring that had already destroyed much of the upper archaeological layers. The 2000 dig exposed the first undercroft, measuring roughly 6.5 metres by 10 metres, its limestone springing stones, the curved blocks from which a vault rises, still in place. Subsequent testing in 2002 opened six further trenches and revealed two additional cellars, each averaging around 6 metres wide and 20 metres long. Among the architectural details recorded were corbels, niches, steps, and the remains of a red-brick arched passageway thought to be associated with the so-called Dutch Billy houses, a style of gabled Dutch-influenced townhouse that once lined Mary Street. Dating the undercrofts precisely has proved difficult, though at least parts appear to belong to the later medieval period, with the vaulted northern undercroft possibly 16th or 17th century.

The site is not a visitor attraction in any formal sense, but it has a quiet afterlife built into the development that replaced it. As part of the agreement with the developers, some of the uncovered features were retained and incorporated as visible elements within the new structure, while the remainder were carefully reburied. Anyone passing along Mary Street today, close to its junction with Fish Lane and the Northern Relief Road, is walking above ground that has been inhabited, built upon, drained, and discarded across several centuries, with a portion of that archaeology now preserved inside the walls of the building above it.