The castle once stood at Snamh dá Ean, meaning “Swim two birds”, a traditional fording point where an island narrows the river channel to about 90 metres. This strategic location served as a recognised boundary marker of Uí Maine, the medieval Irish kingdom, and witnessed one of Ireland’s most consequential political meetings. In 997 AD, a rígdál, or royal conference, took place here between High King Méal Sechlainn of Meath and Brian Boru, King of Munster. Their agreement at this riverside spot ensured cooperation between the two most powerful rulers in Ireland and would shape the political landscape for years to come.

Today, all that remains of the castle is a grass-covered mound of rubble masonry, known locally as the Castle Acre. The mound measures approximately 12.5 by 10.3 metres at its top and rises between half a metre and 1.8 metres high, with the base extending to about 20 by 15 metres. Historical records show that by 1641, the surrounding 500 acres were jointly owned by the Bishops of Meath and Clonfert, though the land had reverted solely to the Bishop of Meath by the 1660s. The castle itself doesn’t appear on the Strafford map of circa 1636, though the road extending west from the Shannon through Cloonburren is clearly marked.

Among the most intriguing finds from the site is a fragment of a medieval graveslab, discovered before 1955 and now housed in the National Museum of Ireland. This broken stone piece, measuring roughly 43 by 38 centimetres and 7 centimetres thick, features an incised cross with circular terminals, circles at the crux, and fleur-de-lis decorations in the angles; a testament to the site’s long religious and cultural significance. Though the castle has crumbled into memory, this riverside location continues to echo with the footsteps of kings and the weight of decisions that helped forge medieval Ireland.