The curving line where the townland of Petitswood meets the townland of Mullingar, running along the south-west arc, has been identified by researcher Paul Gosling as the probable remnant bank of an early ecclesiastical enclosure, roughly 230 metres east to west and 160 metres north to south at its widest points. Ecclesiastical enclosures of this kind, typically a roughly circular or oval earthen bank delimiting a sacred precinct around a church or monastic settlement, are a familiar feature of the early medieval Irish landscape, but they are more often found in rural settings. Here, the enclosure has been swallowed by the modern housing of Auburn Village, and most visitors driving through the estate would have no reason to suspect the geometry beneath them.

The survival is partial but telling. Approximately sixty per cent of the original perimeter can still be traced along the southern and western sectors, where it happens to coincide with the townland boundary, effectively preserving its line through the accident of administrative geography. The northern and eastern sections have not survived on the ground, though their likely course can be extrapolated from what remains. The 1840 edition of the Ordnance Survey six-inch map already shows this curving boundary as the edge of Petitswood, meaning that even by the mid-nineteenth century the feature had been absorbed into the landscape as a property line rather than recognised as an archaeological form. An oblique aerial photograph taken in 1964 captured the curve more legibly, before later development further obscured it. Adding weight to the identification, a feature known as Sunday Well lies just twenty metres to the west of the enclosure; holy wells with day-of-the-week dedications are frequently associated with early ecclesiastical sites in Ireland, their names preserving a memory of communal religious observance that outlasted the structures around them.