Near the motte and bailey at Oldcastle in County Galway, there is a recorded enclosure that, by all accounts, has effectively vanished, and may never have been pinned down with any precision to begin with. A motte and bailey is a form of Norman fortification in which an earthen mound, the motte, is paired with an adjacent enclosed courtyard, the bailey, typically surrounded by a ditch and bank. The enclosure here is something separate again, lying to the east of the motte's fosse, and its existence rests almost entirely on a single early twentieth-century observation.

In 1916, the historian Goddard Henry Orpen recorded what he described as another enclosure situated roughly 38 paces to the east of the fosse of the motte. He noted a ditch some 12 feet, or about 3.6 metres, wide, cutting across the esker, a long gravel ridge formed by glacial meltwater and a common feature of the Irish midlands landscape. Traces of a rampart and ditch appeared to connect this feature back to the motte on both the southern and northern sides, the two lines of earthwork lying approximately 38 paces apart. Despite the careful description, Orpen did not include the enclosure on his own plan of the site. When archaeologists revisited in June 1982, they found nothing. Aerial imagery has equally failed to reveal any trace of it. The enclosure remains unlocated with any certainty.