The combination is odd enough on its own, but the leading explanation for why the enclosure exists at all makes it stranger still: it was most likely built not to defend anything or mark a boundary in the ancient sense, but simply to stop cattle wandering into the turning sails of a working mill.

The windmill was built in 1736 by Marie and Edward Walsh of Borranstown, and its remains still cap the summit at roughly 556 feet above sea level. The enclosure surrounding it is oval in plan, measuring approximately 90 metres north to south and 82 metres east to west, defined by a counterscarp bank, that is, a bank with a ditch on the outer rather than the inner side, standing about 1.8 metres high on its exterior face. A single entrance gap, around 2.5 metres wide, opens to the south. Archaeologists have noted a parallel at the Skerries windmill in the same county, where a comparable enclosure served the same practical purpose of keeping livestock clear of the machinery. That said, the site has also been identified, at least by reputation, with Rath Esa, a place mentioned in the Metrical Dindsenchus, a medieval Irish poem-collection cataloguing the lore attached to significant locations across the country. Whether the earthwork itself has any pre-eighteenth-century origin remains unresolved.

The hilltop rewards the approach partly for what it shows you in every direction: the Hill of Tara is visible to the west, and on a clear day the coast appears to the east. The ground drops steeply on the northern and eastern sides of the enclosure, more gradually to the south and west, so the southern entrance is the more accessible approach. The windmill remains are modest, but their position at the very centre of the enclosure, with the bank running a careful distance around them, gives the whole site an oddly purposeful geometry that only becomes clear once you understand what it was originally designed to protect.