It was not found by excavation or accident, but by community geophysics, a method that uses instruments to detect buried features without breaking the soil. The survey project, called What Lies Beneath, was run by Fingal County Council and documented by Gimson and Garner in 2018, and what it returned was remarkable: a double-ditched enclosure roughly fifty metres in diameter, accompanied by areas of burning, numerous pits, and further ditches, all invisible from ground level.

The enclosure is associated with the sixth-century St Colman, which places its origins in the early medieval period, when such circular ecclesiastical enclosures, defined by one or more surrounding ditches and banks, were a common way of marking sacred ground across Ireland. They are sometimes called cashels when built in stone, but here the boundary was earthen, and only the ghost of it survives underground. The connection to St Colman was not entirely forgotten, even by the nineteenth century. In the 1830s, the scholar John O'Donovan, working for the Ordnance Survey of Ireland on its celebrated letters project, recorded that the ruins of St Colman's church stood to the north-west of Lanistown Castle, a site recorded in the national monument record as DU012-004. O'Donovan was methodical in gathering local knowledge and placename lore as he travelled, and his note preserves a reference that might otherwise have been entirely lost. Adding a further layer of complexity, the enclosure is also cut through by a later landscape feature, two parallel banks and ditches running in a linear course across the site, indicating that the land was reorganised at some subsequent point, possibly during the formal landscaping associated with the demesne itself.

Newbridge Demesne is a public park managed by Fingal County Council, and access is straightforward. The geophysical anomalies lie beneath the surface and there is nothing to see at ground level, but knowing that a buried early Christian enclosure sits somewhere underfoot changes how the landscape reads. Visitors with an interest in landscape archaeology may want to look at the wider setting, noting the relationship between the demesne's later designed features and the older sacred geography beneath them. The site is best visited in winter or early spring, when low-angled light and bare ground make it easier to read subtle variations in topography, though in this case the evidence is genuinely invisible without the aid of instruments.