Historical records from the Civil Survey of 1654-6 paint a vivid picture of the site in its heyday: James, Lord Barron of Dunboyne, an Irish Catholic nobleman, owned the manor, castle, town and lands of Drangan in 1640, though his mother, Ellen Lady Dowager of Dunboyne, was living there at the time. The survey describes not just the principal castle but also a slate-roofed mansion house, a smaller thatched castle tower, and various other thatched houses, all contained within the protective walls of the bawn.

The castle originally stood on a dramatic rocky outcrop, making it both defensible and imposing in the landscape. The first Ordnance Survey map from 1840 shows the bawn as a rectangular enclosure measuring roughly 57 metres north to south and 40 metres east to west, complete with what appears to be a lime kiln at the southwest corner, possibly built into an older circular turret. The southeast corner contained another rectangular feature that likely marked where the keep or main fortified house once stood. Today, the quarrying has dramatically altered the topography; rock faces now drop 20 to 25 metres on the western and northern sides, whilst the eastern edge still maintains its natural steep descent to the river below.

Only fragments of the original structure survive. A limestone wall, roughly 10 metres long and less than a metre high, runs along the northern edge of the quarry, its lime mortar bonding suggesting it could be part of the original castle complex. The wall continues westward for another 14 metres atop the quarried rock face, though much of its facing has collapsed. Local tradition holds that stone from the castle was recycled to build Drangan’s parish church in 1847, which might explain why so little remains visible above ground. An oval depression measuring 22 by 18 metres has been carved out just north of the surviving wall, with quarry spoil piled to the southwest, making it increasingly difficult to trace the original footprint of this once-formidable fortress.