During excavations on Nicholas Street in 1990, archaeologists uncovered the remains of a lime kiln, a type of furnace used to burn limestone at high temperatures to produce quicklime, a material essential for mortar and construction work throughout the medieval period. What makes this particular find remarkable is not the kiln itself, which would have been a fairly ordinary feature of a working town, but where and when it was built.

The kiln had been constructed directly through a deposit of redeposited clays identified as a counterscarp, the outer slope of a defensive ditch that marked the southern boundary of the early town. That the structure cut through this defensive earthwork suggests the area had already lost its military function and was being put to more practical, everyday use. Crucially, the kiln predates the channelling of the River Poddle through this part of the city, an event dated to around 1190 AD, when the watercourse was diverted to serve the needs of the growing urban settlement. The sequence is significant: the kiln came first, the managed river channel came after, placing this small industrial feature in the earliest layers of Dublin's documented urban development. The findings were published by C. Walsh in 1991.

Nicholas Street today runs south from Christ Church Cathedral through what was once the outermost edge of the Viking and early Norman town. There is nothing to see above ground from the 1990 excavation, as the site has long since been built over, but the general area repays a slow walk for anyone interested in Dublin's layered past. The street itself follows a line that has been in use for centuries, and the proximity of the old town ditch, the Poddle's buried course, and the cathedral complex means that a remarkable density of early medieval activity lies just below the pavement. The National Museum of Ireland's archaeology division holds records of many such urban excavations, and published reports from the 1980s and 1990s remain the best guide to what was found during that intensive period of investigation in the city's core.