Also known as Killacollum or Collum Castle, this medieval stronghold was originally recorded in 1201 as being held by Limerick Cathedral. By the 1650s, the castle had become the property of John Haly of Limerick, though it was already described as ruinous, accompanied by just three small cottages. The structure itself was a rectangular tower house measuring roughly 9 metres long and 7 metres wide, featuring a vaulted ground floor, two upper storeys accessed by a spiral staircase, and a distinctive polygonal angle tower on its northwest corner. The castle was protected by a bawn, or fortified enclosure, traces of which have been identified through archaeological excavation.

The castle’s most dramatic moment came during the Cromwellian conquest of Ireland in 1651. Captain Thady Burke and his garrison of fifty men defended Cullam against Sir Hardress Waller’s parliamentary forces. After a brief artillery bombardment using sakers, Burke agreed to surrender. However, in a tragic miscommunication, soldiers stationed on the tower who hadn’t heard of the capitulation opened fire on the English troops entering the gate, killing two and wounding Waller in the left arm. Despite this provocation, Waller showed remarkable restraint and prevented his men from taking revenge on the Irish garrison, contenting himself instead with pillaging the castle and surrounding countryside. The castle later passed to the Marquis of Clanricard before being dismantled by parliamentary forces.

Today, only fragments of Cullam Castle survive; principally a portion of the north wall standing about 2.4 metres high and 6 metres long. Archaeological excavations in 2005 revealed that whilst the west, south and east walls appear to have been demolished in recent times, the original floor of the tower house remains identifiable as a distinctive sandy gravel surface. The excavations also uncovered the earthwork remains of the surrounding bawn, forming an enclosure to the north and east of the tower with a possible entrance to the north. Finds from the site, including pottery sherds and animal bones dating from the 16th to mid 17th century, provide tangible connections to the castle’s period of occupation, when it stood as a significant defensive position along this strategically important river route.