The earliest documented reference to Celbridge’s castle dates from 1403, shortly after the Earl of Kildare acquired the lands between 1397 and 1399, suggesting the stronghold was likely constructed during this period of new ownership. By the time of the Down Survey in 1655–6, the site was recorded as ‘Castletonne Orchard’, featuring a substantial house and orchard, though the original castle was rather modestly described as ‘a hall built after the Irish or country manner, covered with straw’.

The castle’s story becomes intertwined with that of the grand Castletown House estate that would later dominate the area. When Lady Louisa Connolly oversaw the construction of extensive farm buildings in 1787, these new structures were deliberately positioned on the site of the old tower house, incorporating medieval elements into their design. A 2003 architectural survey revealed fascinating survivals from the original castle: a medieval wall built into the east end of the cattle yard and two vaults near the farmyard bell, with the distinctive batter of the extant wall indicating the building once stretched towards what is now the courtyard.

Today, locals know the site as ‘Dongon Castle’, though its medieval bones are largely hidden within the later farm complex. John Rocque’s 18th century map shows a building on the castle site west of Castletown House, surrounded by formal gardens, capturing a moment when the medieval past and Georgian present coexisted. The archaeological footprint of this medieval structure remains traceable, offering tantalising glimpses of a fortified residence that evolved from a thatched hall to a working farm, its stones repurposed but not entirely erased from the landscape.