What makes it unusual is not just its setting but its complexity: rather than a single defensive line, the fort presents three separate banks on the landward side and an additional set of works on the seaward side, as though whoever built it was deeply unconvinced that one barrier would be enough. A promontory fort, for those unfamiliar with the term, is a type of prehistoric or early medieval enclosure that uses a coastal headland as its primary defence, with constructed earthworks closing off the landward approach. The Garden Fort does this with considerable thoroughness.

The landward defences consist of three banks with two rock-cut fosses, a fosse being a defensive ditch, between them. The outermost bank has been partly worn down by a later field boundary, but the inner bank remains the most prominent feature on the site, measuring 7 metres wide and standing 4.5 metres high. The middle bank is flat-topped, 4.5 metres wide at its base and 3 metres high. On the seaward side, roughly 20 metres to the north, a further pair of banks with an intervening fosse closes off much of the headland, though a gap of about 2 metres on the eastern side appears to have served as a causeway through the defences. A separate section of fosse was also cut into the western side of the headland just south of these inner works. The site was recorded by Westropp as early as 1922 and has been noted by several researchers since. More recently, The Discovery Programme carried out geophysical survey work here as part of the LIARI Project, and while one survey area between the outer ditch and middle bank revealed nothing new, a second area to the east of the middle rampart produced responses that may indicate burning, along with a band of subsurface anomalies that could be of archaeological significance.

Lambay Island lies roughly five kilometres off the Dublin coast near Rush, and it is privately owned, which means access requires prior arrangement; visiting independently is not straightforward. The fort sits above steep cliffs at Gouge Point, so the approach on foot demands care. For those who do reach it, the earthworks are well preserved enough to read clearly on the ground, and the layered sequence of banks and ditches rewards a slow circuit rather than a quick look. The possible burning deposit identified by the geophysical survey has not been excavated, so the fort holds questions that remain, for now, unanswered.