The combination is not unique in the Irish landscape, but it is always quietly arresting: a medieval or post-medieval place of worship planted inside a rath, the two structures becoming so entangled over the centuries that the western wall of the chapel has been absorbed directly into the ringfort's inner bank.

A rath is an earthen ringfort, the most common monument type in Ireland, typically built during the early medieval period roughly between the fifth and twelfth centuries as a farmstead enclosure for a family of some local standing. This one at Coolowen is roughly circular, measuring about 26.8 metres north to south and 22 metres east to west, and is defined by an overgrown earthen bank standing around 1.5 metres high. Inside that bank lies a fosse, the technical term for a defensive ditch, and beyond it a very low outer bank, now only about 0.1 metres high, running from the south-southwest to the east-northeast, with faint traces of a further outer fosse beyond that. Three gaps break the inner bank, at the northeast, west-southwest, and west-northwest, the widest of them measuring six metres across. Whether these represent original entrances, later breaks, or a combination of the two is not recorded. What is clear is that at some point the site attracted religious use, and the ruins of the chapel now occupy the interior, its western wall long since merged with the prehistoric earthwork surrounding it.