The reason for the loss is unusually precise: a railway line sliced directly through the site, leaving only the eastern half standing.

A ringfort, or rath, is an enclosed farmstead of the early medieval period, typically defined by one or more circular earthen banks enclosing a domestic area. The Culleen More example was still intact enough in 1837 to be recorded on the Ordnance Survey Fair Plan map as a recognisable oval enclosure, annotated simply as "fort". At some point after that, the Sligo Branch of the Midland Great Western Railway was laid on a north-south alignment, cutting straight through the monument. What remains today is a semi-circular area of roughly 50 metres in diameter from north to south, enclosed by an earthen bank that curves from north-east around to the south-east. The site sits on a south-south-west facing slope with open views across the water, which would have made it a well-chosen position for an early settlement. A field fence running east to west, which also marks the boundary with the neighbouring townland of Portnashangan, intersects the northern perimeter, adding yet another layer of later intervention across the original outline of the fort.

The surviving arc of bank is modest, but the setting on the lakeshore gives some sense of why this particular spot was chosen. The combination of a railway cutting, a townland boundary, and centuries of agricultural use makes this a useful, if quietly melancholy, example of how early monuments accumulate damage incrementally rather than all at once.