Built in the early 1200s, this stone fortress replaced what may have been an earlier earthwork fortification known as the Fort of the Abbot or ‘Liseenabbey’, which the annals record as being burnt in 1135 and again in 1200 when it contained 47 houses. The English constructed their castle here to control the strategic crossing point over the Shannon, with records from 1215 showing Ralph de Derevaus and Walter Reboth as custodians before they were ordered to hand it over to Geoffrey de Mariscis.

The castle’s design reflects classic Anglo-Norman military architecture, comprising a rectangular three-storey stone keep measuring 11.3 by 19 metres, built within an impressive D-shaped earthwork some 32 metres north to south and 37 metres east to west. The defensive earthworks consist of two earthen banks with a wide, flat-bottomed fosse between them, while the keep itself was accessed via a sophisticated forebuilding that housed a drawbridge. This forebuilding, which was still standing when illustrated by Blaymires in 1739, connected to the main entrance at first-floor level; a common defensive feature that forced attackers to climb exposed stairs or ladders to reach the door. The keep’s first floor was lit by narrow slit windows set within widely splayed embrasures, and a spiral staircase in the northwest corner provided access to the upper levels.

What makes this castle particularly intriguing is its apparently short lifespan. The complete absence of any architectural features dating later than the 13th century suggests the fortress may have been undermined and abandoned as early as 1300, during the period of Gaelic resurgence when Anglo-Norman control over much of Ireland began to weaken. Today, only the north and south walls of the keep remain standing, along with portions of the outer courtyard or bawn area to the north, which includes a three-storey gatehouse with its southwest gable still intact, complete with a first-floor garderobe. The site, now designated as National Monument No. 81, offers visitors a glimpse into the turbulent medieval history of the Irish midlands, when control of the Shannon crossing at Clonmacnoise meant control of movement between east and west Ireland.