A large roughly circular enclosure, approximately 126 metres in diameter, appears on the first edition six-inch Ordnance Survey map, but on the ground today there is almost nothing to see. A farm lane traces part of its western and northern limits, and that is largely the extent of what remains visible.

Circular or curvilinear enclosures of this kind are a recurring feature of early Irish ecclesiastical sites, typically indicating the vallum, or boundary, that once separated a monastic or church precinct from the surrounding landscape. What makes Preban particularly interesting is the nested arrangement recorded on the historic map. Within the eastern quadrant of the larger enclosure sat a smaller one, containing a church, and its eastern boundary was shared with the outer enclosure wall. This kind of internal subdivision, where a church and its immediate precinct occupied one portion of a broader sacred or managed space, is a pattern associated with early medieval religious foundations in Ireland, though the specific history of this particular site is not documented in surviving detail. The arrangement implies deliberate organisation rather than organic growth, suggesting the site was laid out according to conventions well established in early Christian Ireland.

The first edition six-inch Ordnance Survey maps, produced in Ireland during the 1830s and 1840s, frequently recorded features that were already fading from the landscape at the time of survey, making them an invaluable record of what had recently been lost. At Preban, the map preserves the outline of an enclosure that the ground itself no longer reveals.