The relationship between the two is easy to miss, and that is partly what makes Caherglassaun worth a moment's attention. Beneath and behind the working farm boundary lies the remnant of a cashel, the term used for a ringfort built from stone rather than earth and timber, a circular enclosure that once defined a defended homestead, likely dating to somewhere between the sixth and twelfth centuries.

The cashel at Caherglassaun measures roughly 34 metres in diameter and is defined by a drystone wall that has largely collapsed. Drystone construction, which uses no mortar, relies entirely on the careful fitting of individual stones, and when it fails it tends to spread outward and flatten over centuries rather than crumbling dramatically. Here, that process is well advanced. The northern arc of the enclosure, from the north-west around through north to east, has left no visible surface trace at all, absorbed into the slope and the pastureland around it. What remains is enough to read the circuit of the original wall, but only just, and the modern field boundary that now follows its line has effectively taken over its role without preserving its substance.

The site sits in ordinary working pasture on a ridge slope, with no formal access or visitor infrastructure. Its survival is partial and its appearance unremarkable to anyone not looking carefully for the slight irregularities in the ground and the change in character where old stone meets newer coursing in the field wall above it.