In 1580, Cathbarr O’Donnell drew his last breath within these walls, an event significant enough to be recorded in the Annals of the Four Masters. The castle’s strategic position wasn’t accidental; it was built to guard Scairbh Sholais, an important ford across the river, and it’s from this crossing point that the castle took its name.

By the mid-17th century, the fortress had already fallen into decline. The Civil Survey of 1654-6 refers to it merely as the ‘old Castle of Scarsolus’, suggesting its military importance had long since waned. The structure managed to survive, albeit in increasingly ruinous condition, until the early 19th century when local residents dismantled what remained of the medieval stonework, likely repurposing the materials for more practical construction projects.

Today, visitors to the area will find no visible trace of Castle Sollus, though its approximate location near Ardahee can still be identified. The site represents one of many lost castles that once dotted the Donegal landscape, serving as reminders of the region’s turbulent past when control of river crossings and territorial boundaries required constant vigilance. Archaeological surveys have documented its existence and significance, ensuring that whilst the physical structure has vanished, its place in Irish history remains preserved.