The southern bank of a rath, one of the circular enclosures of compacted earth that were built across Ireland throughout the early medieval period as farmstead boundaries, was at some point adapted to incorporate a limekiln. The kiln, a structure used for burning limestone at high temperatures to produce quicklime for agricultural soil improvement or building mortar, was essentially folded into the prehistoric earthwork rather than constructed beside it.

The detail comes from the 1997 Archaeological Inventory of County Cork, which catalogues the rath at Garranereagh and notes, almost in passing, that its southern bank contains the remains of the kiln. It is recorded as a subsidiary feature of the rath entry rather than a site in its own right, which gives some sense of how incidental its survival was considered. Whoever built or used the kiln clearly found the existing raised bank a convenient structure, perhaps as shelter or simply as a ready-made mass of earth against which to set the kiln's stone chamber. The practice of reusing older landscape features for later agricultural purposes was common throughout rural Ireland, but the combination here, a rath absorbing a limekiln into its own fabric, is an unusually literal layering of different centuries.