These thick stone walls, measuring 1.35 metres across, are the remnants of one of two guest houses built around 1577 between Ennis Friary and the River Fergus. The houses were constructed to accommodate visitors to the friary, and one eventually became known as the Earl of Thomond’s house. Today, this two-storey structure survives as a return in a later building, its original features still visible in the form of a high window in the western wall and a blocked segmental arch that likely once held a fireplace.

The building’s history traces the fortunes of some of Clare’s most prominent families. In 1672, Donough O’Brien of Leamaneh leased a small turret here along with a boat slip, both described as parcels of the former Abbey of Ennis. By 1682, records refer to it as the ‘old decaying house of the earl of Thomond’, suggesting its grandeur had already begun to fade. Despite its deterioration, the property remained in O’Brien hands; Donough bequeathed what he called the ‘castle of Ennis’ to his grandson Edward O’Brien of Dromoland in his 1717 will.

Most of the riverside castle was demolished around 1835, with its stones possibly recycled for the construction of Club Bridge about 100 metres to the north, though no medieval stonework is visible in the bridge today. The surviving section wasn’t properly documented until April 2013, when an Environmental Impact Statement for the Fergus River flood relief scheme noted these medieval remnants. The structure measures 9.75 metres east to west and 7 metres north to south, a modest but tangible link to Ennis’s medieval past and the days when Franciscan friars and Irish nobility shaped the town’s character.