Built in the early 16th century, this formidable structure was one of a pair of fortifications that guarded each end of the medieval bridge, with its twin standing on the County Clare side. The townland where it stands, now called Montpelier, was once known as Portcrushy, as shown on 17th century Down Survey maps. The castle’s location was crucial; it controlled access to a bridge that had likely existed in various forms, whether stone or timber, since medieval times.

The castle’s moment of fame came in 1536 when English forces arrived to find it defending the bridge alongside its Clare counterpart. Contemporary accounts paint a vivid picture of the siege: the Limerick castle was described as “buylded all of hewen marbell” with walls an impressive 12 or 13 feet thick, standing within the water itself, somewhat distant from the land. The English brought their ordnance to bear on the structure, firing at it throughout the day, but the massive walls proved nearly impervious to cannon fire. The defenders, a mix of gunners, gallowglasses and horsemen, had fortified their position with timber and hogsheads filled with earth. Despite its strength, the castle fell the following day when English forces used fascines, essentially bundles of sticks, to fill the water between the land and the castle, then scaled the bridge with ladders, forcing the defenders to flee.

By 1650, when Parliamentary forces arrived during Cromwell’s Irish campaign, the castle was already reduced to “the stump of an old castle” standing in the water. Captain Draper’s men seized both this ruin and the remains of a house on the opposite shore, using them as staging points to establish a crossing. They fastened long ropes across the river to tow boats over, successfully landing 500 men on the Thomond side within an hour. Today’s multi-period stone bridge, first constructed in the late 17th century, stands where these dramatic events unfolded, though the medieval castles that once commanded this vital crossing point have long since vanished beneath the waters of time.