The arrangement is a quietly odd one, a structure from the early nineteenth century grafted onto a fabric several centuries older, the whole complex sitting just west of Beagh Quay with the estuary spread out below. The blockhouse was designed as a bombproof barrack, meaning its vaulted roof was robust enough to serve as a gun platform while the ground floor provided defended accommodation for a garrison. It is one of several such installations that monitored the Shannon during the period of Napoleonic anxiety about a French landing on Irish soil.

The tower house itself was probably built by the Fitzgerald family, the Knights of Glin, who controlled this stretch of the Clare and Limerick shoreline in the sixteenth century. Their tenure ended in 1578 when the land was confiscated and granted to Sir W. Drury, according to the antiquary T. J. Westropp writing in the early twentieth century. By the time of the Civil Survey of 1654 to 1656, the castle was already described as ruinous, and the two townlands of Beahy and Ballynehagulshy were in the possession of Major General Sir Hardress Waller. That survey, a detailed accounting of Irish land ownership carried out under the Cromwellian administration, noted not only the castle and two dwelling houses but also fifteen cottages and a salmon weir seat on the Shannon, suggesting the site remained economically significant even in its dilapidated state. The southern side of what is now a poorly preserved nineteenth-century courtyard has since been replaced by a row of cottages and outbuildings, some of which may date to the seventeenth century.

The site sits close to Beagh Quay on the Limerick side of the Shannon, and the remains include the four-storey tower house, the three-vaulted-apartment blockhouse attached to its western wall, and a level platform at the base of the northern wall, built out over the creviced cliff face. The courtyard enclosure is fragmentary. The vaulted stonework of the Napoleonic battery is the most legible element; it is worth looking closely at how the later military structure was simply built against the existing medieval masonry rather than replacing it, two different moments of strategic thinking about the same stretch of water made visible in the same wall.