The site consists of a roughly circular area bounded by what remains of a stone wall, now heavily overgrown with vegetation and partially collapsed through centuries of weathering and neglect. Despite its deteriorated state, the enclosure still holds its basic form, allowing visitors to trace the original boundary and imagine how it might have appeared when first constructed.

The most intriguing feature of this site is found along its northern perimeter, where a large boulder has been incorporated into the wall structure. This boulder bears seven cupmarks; small, circular depressions deliberately carved into the stone surface. Cupmarks are amongst the most common forms of prehistoric rock art found across Ireland and Britain, typically dating from the Neolithic to the Bronze Age periods. Their exact purpose remains one of archaeology's enduring mysteries, with theories ranging from territorial markers to ritual sites, astronomical calendars, or even primitive maps.

The enclosure at Castlebane represents just one of many such sites scattered across County Donegal, a region particularly rich in prehistoric monuments. The combination of the stone enclosure with decorated rock art suggests this location held special significance for the people who created it, though whether it served as a ceremonial space, a defended homestead, or something else entirely remains unknown. Today, visitors who make the effort to find this overgrown site can still make out the cupmarks on the northern boulder, these simple yet evocative symbols connecting us directly to the hands that carved them thousands of years ago.