A drumlin is a smooth, elongated hill shaped by glacial action, and in Ireland such ridges were often chosen for early enclosed settlements, offering natural elevation and visibility. At Knockreagh, an oval earthwork once sat on the summit of one such ridge, measuring roughly 35 metres along its longer axis and just over 26 metres across. By the time anyone recorded it in careful detail, in 1968, it was already a grass-covered remnant, its bank planted with trees and faced on the outside with stone, with a drain running around much of its perimeter. The original entrance, about two and a half metres wide at the base, faced south-east.

What makes this site particularly telling is what happened next. When surveyors returned around the year 2000, sections of the bank had been removed altogether along the north-north-west to south-east line, and elsewhere the earthwork had been absorbed into an ordinary field boundary, its stones and earth pressed into service as a hedge and bank. The enclosure, which had survived long enough to be formally described and measured, had by then been partially dismantled and repurposed by the working of the land around it. The outer fosse, the defensive ditch that typically accompanies such enclosures, was already absent in 1968, suggesting the site had been losing its definition for considerably longer than the twentieth century alone.