The change in its circumstances is part of what makes it quietly remarkable. When the Ordnance Survey first mapped this part of the midlands in 1837, the feature appeared clearly as an island, sitting roughly 180 metres east of the western shoreline, with Dysart Island visible some 420 metres to the south-southeast. By the time a revised edition of that same map was produced in 1911, it was being called Ash Island. Today, falling lake levels and land drainage have left it entirely high and dry, smothered in trees and barely legible as anything other than a slight rise in the vegetation.

What lies beneath the overgrowth is almost certainly a crannóg, a type of artificial or partially artificial island used as a settlement platform from the early medieval period onwards, typically built out into shallow water using layers of timber, peat, stone, and brushwood. Researcher Aidan O'Sullivan, writing in 2004, described the site as a low, oval cairn of stones and earth measuring approximately 30 metres north to south and 30 metres east to west, rising to about 2 metres in height, with additional stones scattered around its edges. The mound slopes down gradually on all sides, and the whole structure was originally set in shallow open water to the north of Dysart Island. O'Sullivan classified it as a probable crannóg, potentially of early medieval date, though no excavation has established that with certainty. The disconnection between its original watery setting and its current landlocked condition means it no longer reads as what it once was, a deliberate construction positioned in a lake, likely chosen for the defensive and social advantages that isolation could provide.