The castle once stood on the southeastern side of the Mullet peninsula, bordered by marshy flatland to the northwest and north. Today, visitors can access the site by walking roughly 100 metres along the beach towards the east or northeast, where the ground rises and becomes drier underfoot.

Historical maps paint a picture of what once was; the 1838 Ordnance Survey six inch map shows a rectangular building measuring about 20 metres from east northeast to west southwest and 10 metres from north northwest to south southeast, already noted as ‘Barranagh Castle in ruins’. By 1921, only a single wall running parallel to the shore remained standing. Where the castle once dominated the landscape, there’s now just a gentle, grass covered rise, perhaps 12 to 20 metres across, surrounded by a scatter of large angular stones that spill onto the rounded cobbles of the beach. Among this rubble lie two substantial blocks of displaced masonry, each about two metres by one metre, held together with rough lime mortar packed with shells and fragments of animal bone.

The most intriguing remnants include what might be the basal course of a wall; two parallel lines of stones set two metres apart, extending westward for about eight to ten metres. The eroding southern edge reveals a layer of dark soil mixed with degraded mortar and small, angular stones, some showing signs of burning, which could be either an old floor surface or remnants of a limekiln that locals say was built within the castle ruins before storms destroyed it. Among the scattered stones lies a particularly evocative find; half of a rotary quern’s upper stone, its D shaped form still showing the central hole where grain would have been poured, and a smaller hole near the edge where a wooden handle once turned this ancient grinding tool.