According to the 1659 Down Survey parish map of Leny, these twin fortifications stood sentinel beside a medieval bridge, controlling an important routeway that connected the towns of Mullingar and Longford. The survey’s terrier specifically noted ‘at Ballinilack two Castles & a Bridge upon the River Ighny’, placing these structures amongst six castles recorded in the parish, which also included single fortifications at Rathbennett, Farrow, Cullanhue and Ballinafid.

Historical maps suggest the castles were positioned strategically on either side of the road approaching the bridge; one to the north and another to the south. The 1837 Ordnance Survey Fair Plan shows a small rectangular building within what may have been a walled enclosure or bawn in the eastern quarter of the site. This structure, which stood between a building later known as ‘The Bridge House’ and the river itself, has since been levelled, though a scarped mound or hillock still marks its location. Today, visitors to the area will find only subtle earthworks and a raised, flattened area of ground with some protruding stones atop a modified hill, which likely represents the remains of one of these medieval strongholds.

Archaeological surveys over the years have revealed how much the landscape has changed since medieval times. When inspected in 1983, investigators found no visible castle remains, noting that debris from the Inny drainage scheme had likely obscured any wall footings. A more recent survey in 2012 identified the raised ground as an irregular shaped area, better defined on its northern side, though nothing substantial enough to classify definitively as either castle or burial monument. These ghostly earthworks, combined with cartographic evidence, are all that remain of Ballinalack’s twin guardians, which once protected this vital river crossing in medieval Ireland.