Nobody is entirely sure where. The 1842 Ordnance Survey six-inch map marked the site with a broken circle roughly twenty metres in diameter and labelled it 'Legan Abbey and Tower', which suggests that cartographers of the time had at least a general sense of its position. But the broken circle is itself a qualification, a cartographic admission of uncertainty, and no visible trace of any structure survives above ground today.

The Benedictines were a monastic order following the Rule of Saint Benedict, and their houses in medieval Ireland ranged from substantial abbeys to very modest establishments. This one, according to the ecclesiastical historians Aubrey Gwynn and R. Neville Hadcock, was a small non-conventual priory, meaning it lacked the full complement of monks required to operate as an independent community under a prior. They place its founding at 1204 or later, situating it in the period of Anglo-Norman consolidation in Munster, when new religious foundations of various sizes were being planted across the region. A researcher named Hurst, writing in 1925, examined the question of the abbey's exact location and found it similarly unresolved.

What makes this place notable is precisely its elusiveness. The name Monkstown almost certainly preserves a memory of the foundation, a common pattern in Irish placenames where the monks themselves have long since gone but their presence lingers in the townland. Beyond that echo and a cartographer's tentative circle, there is very little left to find.