During the 17th century, this land was home to a castle and six other dwellings, all held by the Barnewall family, one of Dublin’s prominent Anglo-Norman dynasties. The estate’s fortunes shifted at the century’s close when Major Deane of Crumlin, a military man with grand ambitions, demolished the old structures and erected a mansion in their place. This became his residence until 1699, marking a new chapter in the property’s long story.

The mansion underwent significant transformation in 1787, when it was completely rebuilt as Terenure House, reflecting the Georgian architectural tastes of the period. This rebuilding was so thorough that no trace of the earlier structures survived; neither the medieval castle of the Barnewalls nor Major Deane’s late 17th-century mansion left any identifiable features in the building that followed. Today, Terenure College occupies these historic grounds, its modern educational purpose built quite literally upon layers of Dublin’s past.

Archaeological surveys and historical records, compiled by researcher Geraldine Stout and documented by scholars like Mac Giolla-Phadraig, have pieced together this narrative from various sources, including Simington’s detailed land surveys from 1945. While the physical remnants of the castle and early mansion have vanished, their story remains an intriguing reminder of how Dublin’s suburban landscapes conceal remarkable histories beneath their everyday appearances.