Located at the northern end of a rocky bluff, just eight metres south of an inland promontory fort, this medieval stronghold once commanded views over the surrounding countryside. The 1838 Ordnance Survey map depicts it as a rectangular building measuring approximately five metres north to south and fifteen metres east to west, but today only subtle changes in vegetation growth reveal the roughly square footprint where the castle once stood.

According to local memory, low stone walls marked the site well into the twentieth century, serving as the last tangible remnants of what was once a formidable structure. These final traces were removed around the 1950s, likely repurposed for field boundaries or farm buildings, a common fate for many of Ireland’s lesser castle ruins. The removal of these walls completed the castle’s transformation from physical monument to archaeological memory, leaving researchers to piece together its history from maps, records, and the faint impressions it left on the earth.

The castle takes its name from the nearby Douglas River, suggesting the waterway played an important role in the site’s strategic value or perhaps in defining territorial boundaries. While the exact date of the castle’s construction remains uncertain, its proximity to the promontory fort hints at a location that held defensive significance across multiple periods of Irish history. Today, visitors to the site need a keen eye and perhaps a bit of imagination to trace the outline of Castle Douglas amongst the pasture grasses, where cattle now graze over the foundations of what was once a symbol of power and control in medieval Sligo.