While most of the island consists of rocky outcrops, its western side features a remarkably level, sheltered strip measuring about 120 metres north to south and between 15 to 25 metres wide. An earthen bank, reaching up to a metre in height and three metres in width, runs along the cliff edge of this strip, extending to the rock outcrop at its northern end. Intriguingly, this bank appears to have been constructed after the island separated from the mainland, suggesting deliberate fortification of what was already a naturally defensive position.

The strip contains several intriguing archaeological features that hint at past habitation. About 10 metres from the northern end, archaeologists have identified a rectangular foundation measuring three metres north to south and seven metres east to west internally, defined by low banks about 20 centimetres high and up to 1.5 metres wide. Twenty metres south lies what appears to be half of a second foundation of similar size and alignment, whilst another foundation, measuring eight by six metres overall, sits nine metres further south. Additional stretches of banking that don't form any clear pattern have also been noted across the site. Perhaps most tellingly, a water filled hole, possibly an ancient well, can be found 15 metres south of the last foundation, adjacent to the eastern rock outcrop that bounds the strip.

Local tradition holds that this naturally fortified island served as a refuge for the O'Donnell clan during the 16th century, a claim that seems entirely plausible given the defensive advantages of the site. With sheer cliff edges providing natural protection on most sides and evidence of substantial construction work on the only accessible strip of land, Dooanmore would have made an ideal stronghold during troubled times. The combination of defensive earthworks, multiple building foundations, and what may be a well all point to this being more than just a temporary hideaway; it appears to have been a deliberately chosen and carefully prepared refuge, ready to shelter its inhabitants when danger threatened from the mainland.