That is not something most early medieval enclosures can claim. The cashel at Baile An Ghlaisín sits on the lower southern slopes of the mountain ridge running east from Lough Anascaul in County Kerry, occupying wet pastureland with a clear outlook over the Anascaul valley. A cashel is a stone-walled ringfort, the dry-built equivalent of the more familiar earthen rath, and this one measures roughly 30 metres north to south and 33 metres east to west. For much of its existence it was effectively invisible on paper: the second edition of the Ordnance Survey map recorded no monument here at all, only a slight curve in the townland boundary that happened to trace the line of the buried wall.

The enclosing wall has collapsed into a spread of rubble roughly 5.7 metres wide, its inner face entirely obscured, though a single course of the outer face can still be followed around most of the circumference, and in the south-east quadrant it survives to a height of about 0.85 metres. On the western side, a modern field wall has been laid directly on top of the old cashel wall, which now forms part of the townland boundary itself. Inside the enclosure, two rectangular house platforms survive, both built of dry-laid stone and both abutting the cashel wall. The larger of the two measures 8.3 by 5.3 metres internally and once had opposing doorways in its north and south walls, though both are now too damaged to read clearly. A souterrain, an underground dry-stone passage used in early medieval Ireland for storage or refuge, occupies the north-east sector of the interior. It consists of two connected passages or chambers: one running roughly north-north-east to south-south-west, possibly extending beneath the cashel wall itself, and a second branching south-west for at least 5.5 metres. The passages are now blocked and inaccessible, but can be partially glimpsed through a gap beneath one of the roofing slabs. The stream that once ran along the outside of the north-east section of the cashel wall has since shifted its course underground, threading through part of the souterrain before re-emerging to the east-south-east of the enclosure, as though the monument had quietly absorbed the landscape around it.