The southern of the pair is a cashel, a type of ringfort built from drystone rather than earthen banks, its circular wall enclosing a space roughly 33.5 metres across. Where an earthen ringfort relies on compacted soil and ditches to define its boundary, a cashel achieves the same effect in stone, a method well suited to areas of Connacht where rock is plentiful and good digging ground is not.

The wall here survives best along its south-eastern arc, continuing through west and round to north, giving a strong sense of the original circuit even where sections have collapsed or been robbed for later use. What makes the site quietly interesting beyond its own structure is the way the surrounding landscape has grown around it. Field walls, the kind of low drystone boundaries that divide agricultural ground across the west of Ireland, radiate outward from the monument at its northern and south-eastern sides. This is a common enough phenomenon near ancient enclosures; later farmers, working the land over centuries, often found it practical to anchor their own boundaries to whatever substantial stonework was already standing. The cashel, in that sense, became a kind of pivot point in the local field system, its presence shaping land use long after its original purpose had been forgotten.

The site sits about a hundred metres south of a second ringfort, and the proximity of the two monuments is the kind of detail that archaeologists find worth noting without necessarily being able to explain. Paired or clustered enclosures appear elsewhere in Ireland and may reflect family groups, territorial divisions, or sequential occupation across generations, though no specific evidence bearing on Drumbulcaun has been published to settle the question.