What appears on the 1836 Ordnance Survey map as a substantial structure, roughly 10 metres square and marked in gothic lettering as “Ardagh Castle in ruins”, has now been reduced to a single surviving wall. This remaining section, measuring 8 metres long, 1.2 metres wide and just 1 metre high, runs northeast to southwest, with faint traces suggesting the wall once extended another 16 metres to the northeast.

The castle’s history is somewhat enigmatic, though records from 1640 reveal that the entire parish of Ardagh, including 114 acres in the Manor of Ardagh, belonged to the Lord of Slane. Curiously, whilst the ownership is clear, no tenant’s name was recorded in the historical documents compiled by Simington in 1940, leaving questions about who actually occupied and managed the castle during its active years.

Today, visitors to the site will find the solitary wall fragment surrounded by grass-covered quarries, evidence of the area’s industrial past that followed the castle’s decline. The location at the crest of the slope would have provided strategic advantages in its heyday, offering commanding views across the surrounding countryside; a practical choice for a fortified residence that now exists mainly in archaeological records and old maps.