That is a quiet kind of erasure: a fort designed, built, garrisoned, added to, and then simply abandoned, leaving almost nothing legible behind.

The island, which sits between Great Island and Ringaskiddy, may carry traces of even earlier occupation in its name, with scholars suggesting a possible Viking presence reflected in the etymology. The earliest confirmed fortification, however, dates to the summer of 1602, when work began to a design by the military engineer Paul Ive. Bastioned forts of this period used projecting angular platforms, known as bastions, to allow defenders to cover the full length of a wall and eliminate blind spots; Ive's design was an irregular quadrangular work with demi-bastions along the northern cliff edge and full bastions at the two southern corners. Soldiers were garrisoned there by October 1602, yet by March 1603 the fort was still unfinished. A keep and gatehouse followed between 1608 and 1611, but by 1624 the fort had been abandoned, and it remained in disrepair for the rest of the seventeenth and eighteenth centuries. When researchers examined the site in the late twentieth century, they found the area had been subject to so much disturbance that the keep, once described as standing around fifteen feet in height, had effectively ceased to be a readable ruin.

The island's later history layered over it comprehensively. In 1806 it was formally divided between the Ordnance and the Navy, the boundary marked by a high stone wall. The Ordnance side, to the west, received a Martello tower built on the high ground roughly where Ive's fort had stood; a Martello tower is a small circular defensive structure, a form widely constructed around the Irish and British coasts during the Napoleonic period. The Navy developed a victualling yard to the east, its six large warehouses still standing alongside other early nineteenth-century buildings that appear on the 1842 Ordnance Survey map. A dockyard followed on reclaimed ground between 1865 and 1887. The island today is shared between the Irish Naval Service and Irish Steel, which means the whole accumulated landscape, Elizabethan ghost, Napoleonic infrastructure, Victorian dockyard and all, remains largely beyond casual reach.