The square enclosure, measuring approximately 30 metres on each side, appears as a cropmark in cultivated fields; a subtle difference in vegetation growth that traces the path of an ancient water-filled ditch long since filled in. These marks are best spotted from above, particularly visible on Bing Maps’ aerial view, where centuries-old earthworks reveal themselves through the varying colours and heights of modern crops.

Moated sites like this one were a common feature of the medieval Irish landscape, particularly from the 13th to 15th centuries. They typically consisted of a raised platform surrounded by a water-filled ditch, or fosse, which served both defensive and status purposes. The occupants, often Anglo-Norman settlers or prosperous farming families, would have built their timber or stone dwellings within the protected square, using the moat to deter both human intruders and wild animals whilst also demonstrating their social standing in the community.

Today, nothing remains visible at ground level in Rathsillagh Upper; the site has been completely levelled by centuries of agricultural activity. Yet from the air, the filled-in fosse continues to affect drainage and soil composition, causing crops to grow differently along its path. This phenomenon allows archaeologists to map medieval settlements that would otherwise be lost to history, offering a window into how people lived, farmed, and defended themselves in medieval Kildare. The site was identified by P. Reid and catalogued by Gearóid Conroy in November 2014, adding another piece to our understanding of Ireland’s medieval settlement patterns.