At Castleross, not even foundations remain of what was once a substantial structure. When antiquarians Davies and Swan surveyed the area in 1939, they could still make out the castle’s foundations, though the building itself had been demolished some 90 years earlier. Today, visitors would find no visible trace whatsoever; the site has been completely reclaimed by the surrounding fields, leaving only historical records to mark where this defensive structure once stood.

The castle at Muineagh in the townland of Desertegny presents a similar tale of lost heritage. Classified simply as an ‘unclassified castle’ in archaeological surveys, it represents one of many such fortifications that once dotted the Donegal landscape. These structures, likely dating from the medieval period through to the 17th century, served as both defensive positions and symbols of authority for local lords and landowners. The lack of detailed historical records for many of these sites speaks to their relatively modest scale; they were working fortifications rather than grand seats of power.

Both sites were documented as part of the comprehensive Archaeological Survey of County Donegal, compiled by Brian Lacey and his team in 1983. This survey, which catalogued field antiquities from the Mesolithic period through to the 17th century, serves as a crucial record for sites like these that have left little or no physical trace. Without such documentation, these castles would be entirely forgotten, their locations known only through place names that hint at a more fortified past. For those interested in Ireland’s medieval heritage, these invisible castles serve as reminders that the landscape once bristled with far more fortifications than survive today, each one a node in the complex network of power and defence that characterised medieval and early modern Ireland.