This rectangular enclosure, which appears on the 1838 Ordnance Survey map but vanishes from later editions, measured approximately 30 metres east to west and 20 to 25 metres north to south. Today, only subtle clues remain: a low stony scarp on the western side, a band of nettles marking the southern boundary along the castle mound, and fragments of the original walls incorporated into a modern field boundary.

The most substantial remnants of this possible bawn survive along its northern edge, where two sections of the original wall are visible beneath a later drystone field wall. The western portion reveals itself as a slumped bank of earth and stone, roughly 8 metres long and just under a metre high, with what appears to be the wall’s core still discernible; two rough courses of large stones rest atop a thin horizontal slab at its base. The eastern section, stretching nearly 8 metres, shows two or three courses of rough stone blocks packed with earth, topped by a layer of sod upon which the current field wall sits.

While the eastern side of the enclosure is barely perceptible today, these surviving fragments offer tantalising evidence of a defensive structure that once stood guard near the castle. Bawns were fortified enclosures typically built to protect livestock and provide a defensive courtyard for tower houses and castles during the plantation period and beyond. This example at Knockalegan, though largely erased by time and agricultural activity, represents an important piece of Mayo’s defensive heritage, its stones gradually being absorbed back into the working landscape of rural Ireland.