The cairn, a prehistoric monument type built from piled stone rather than earth, rises nine metres and measures twenty-seven metres across its base, but the figures alone do not quite capture the effect. Because the outcrop beneath it climbs steeply on its southern face and drops to a natural ledge on the north, the monument appears considerably larger than it is. The island itself amplifies the illusion; there is nothing nearby to offer scale, and the cairn looks out over the western end of Lambay with a commanding unobstructed view.

The monument has attracted scholarly attention for some time, noted by Westropp as far back as 1922 and examined more recently by Gabriel Cooney, whose work appears in publications from 1993 and 2009. One curiosity is the narrow flat top, which researchers have suggested may not be an original feature of the cairn's design. The most likely explanation, noted by Westropp, is that a trigonometrical station, a surveying marker used in the systematic mapping of the landscape, was inserted into the summit at some point, shaping the profile in the process. Despite what the monument's size might suggest, a geophysical survey transect carried out across the cairn revealed no internal structures, leaving its inner arrangement, and its original purpose, genuinely uncertain. There are no kerbstones visible around the base, which distinguishes it from many cairns of comparable scale elsewhere in Ireland.

Lambay Island lies roughly four kilometres off the Dublin coast near Rush and is privately owned, meaning access is not straightforward. Visitors should establish permissions well in advance and should not assume any right of landing. Those who do reach the island will find the cairn on its northern side at the highest point of the terrain, where the rock outcrop makes the ascent feel more exposed than the modest elevation might suggest. The loose boulders visible through the grass covering are worth noting carefully underfoot. The view westward across the island from the summit is extensive, and it is easy to understand, standing there, why whoever built this chose the spot.