A cashel is a type of ringfort defined by a stone wall rather than an earthen bank, and this one, known as Cathair Bheag, meaning "small stone fort", is a quietly peculiar survival. By 1901 the antiquarian T. J. Westropp thought it was nearly gone. Over a century later, its walls still stand up to two metres high in places, with both inner and outer facing stones intact.

Westropp returned to the site in 1915, sketching the walling and noting that it formed part of "a curious group of ring walls". He described the construction as "large shapely blocks with many upright joints", and recorded that the gateway faced south, though only its western pier still stood at that time. The original entrance gap at the south survives to this day. The cashel encloses a roughly circular interior of around 20 metres east to west and 17 metres north to south, and that interior slopes gently downward toward the east. Within it, in the north-east sector, sits a D-shaped enclosure whose date and purpose remain uncertain. Niches are cut into the inner face of the wall in the north sector and into the outer face near the east-south-east, though what function they served is not recorded. A later field wall was at some point built along the original line of the cashel, blurring its outline in sections, and the whole site sits within a broader field system on the mountain. The site appeared on Ordnance Survey maps as early as 1842 and was still being mapped by Tim Robinson in 1977 under its Irish name.

The cashel is set on a terrace with higher ground rising to the south and west, which gives the enclosure a slightly sheltered quality despite its exposed altitude. A second enclosure lies roughly 71 metres to the north-north-east, suggesting this part of the mountain supported a more organised, perhaps even clustered, pattern of early settlement than its remote position might imply.