That detail, almost casual in its indifference to the past, tells you something about how early medieval monuments tend to fare in the Irish landscape. The site is a cashel, a type of ringfort built from drystone rather than earthen banks, and its circular wall, once perhaps shoulder-height or taller, has long since collapsed into the undergrowth and been swallowed by vegetation.

The cashel measures roughly 33.2 metres in diameter, a figure recorded by J. Fahey in 1893, and it is the most precise thing we can say about it with confidence. Cashels of this kind were typically enclosed farmsteads of the early medieval period, the stone equivalent of the earthen raths found across Ireland, built to define a household's territory and provide some degree of protection for people and livestock. At Sheeaun, that enclosing wall is now so thoroughly collapsed and overgrown that the circuit is more inferred than seen, with a later agricultural field wall cutting through it from the south-east. The result is a monument that has been partly cannibalised by the very landscape it once organised.