When excavation work was carried out in 2001 to the rear of numbers 59 to 64, archaeologists working within the church building and its adjoining hall found something the congregation above almost certainly had no reason to expect: the remains of an earlier Dublin, pressed quietly into the ground beneath them.

The excavations uncovered the foundations of two limestone walls, dated to somewhere between 1600 and 1650, placing their construction in the decades before the Cromwellian upheaval reshaped so much of Irish urban life. Limestone was the standard building material of the period in this part of the city, and foundations of this kind are the structural bones of houses, outbuildings, or enclosures that would otherwise have left no trace above ground. Just outside the formal site boundary, part of a brick-built house from the 17th century was also identified, suggesting a small cluster of early modern domestic activity in what is now a busy stretch of the old city's southside. The findings were recorded and published by archaeologist Linzi Simpson in 2003.

Great George's Street South runs south from Dame Street and is a well-travelled part of the city, familiar enough that the archaeological layer beneath it tends to go unnoticed. There is nothing visible at street level to mark where the walls were found, and the church itself is a functioning place of worship rather than a heritage site. The interest here is less in what a visitor can see and more in what the record tells us: that the ground beneath this particular stretch of Georgian and Victorian streetscape carries an earlier imprint, one laid down when this part of Dublin was still taking shape in the first half of the seventeenth century.