At the eastern tip of a raised island of ground in the middle of the Bog of Allen, a cluster of enclosures, stones, and earthworks marks the site of one of Kildare's older ecclesiastical settlements, its details almost swallowed now by poor preservation and the creeping flatness of the surrounding bog. What makes the place quietly arresting is not any single dramatic feature but the layering: a large D-shaped outer enclosure contains a smaller, irregular one, which in turn holds the traces of a church site and graveyard, with a rectangular enclosure abutting the south and the outlines of a possible field system to the north. Scattered among these remains are a bullaun, a roughly circular stone basin hollowed out by hand and associated across Ireland with early Christian and pre-Christian ritual use, along with three cross-inscribed stones still on site.

The settlement at Lullymore, known in early sources as Lilcach, appears in the historical record through a handful of terse annalistic notices. Gwynn and Hadcock note that St Erc, bishop of Lilcach and Slane, died in 512; that a figure recorded as The Gall from Lilcach died in 730; and that Cuan, described as an anchorite, a solitary monk living apart from a wider community, died in 748. These brief entries point to a site with genuine early medieval significance, even if the physical remains are now difficult to read. Lullymore itself is not a true island but a sub-circular area of higher ground, roughly two kilometres across, rising from the surrounding bog. Before modern roads reached it from the east and west, the settlement was connected to higher ground to the north and south by toghers, the raised timber trackways that served as causeways across bogland and which are themselves a recurring feature of the Irish midlands. Several of the cross-inscribed stones and two small stone crosses that originally stood in the graveyard were removed and incorporated into a memorial, erected around 1798, roughly 600 metres to the northwest in Lullymore West; a further cross-inscribed stone from the same graveyard is now held in the Bog of Allen Nature Centre Museum.

The site sits within the bog landscape rather than above it in any obvious way, and the enclosure remains are poorly preserved at ground level, making aerial photographs, including a series taken between 1966 and 1971, more revealing than a ground-level visit. A holy well associated with the site has not been located. Those who do come should look for the bullaun and the three remaining cross-inscribed stones, and bear in mind that much of what defined this place, its stones, its water source, its community of use, has quietly dispersed into the surrounding landscape over the past twelve centuries.