The ruins at Killahane are heavily overgrown now, the limestone walls reduced to rough, random-coursed remnants, but the broader shape of the enterprise is still readable in the landscape if you know what to look for.

The mills here were established in the late sixteenth century by the Browne family of Molahiffe House, a landed family whose principal seat lay not far away. By the time Samuel Lewis was compiling his topographical dictionary of Ireland in 1837, he could still record two distinct operations at Firies: a small flour-mill and a tuck-mill. A tuck-mill, also known as a fulling mill, was used to process woollen cloth by pounding it with water-driven hammers, cleaning and thickening the fibres; the fact that both grain and cloth were being processed here suggests a small but reasonably diversified local economy. The most legible survival today is the millrace, the channel that once directed water to power the mill wheel. Here it survives as two low parallel earthen banks, the kind of feature that registers as little more than a slight unevenness underfoot but which once carried the functional heart of the whole site.

The ruins sit roughly one kilometre northwest of Firies, spread across both sides of the road. The western side holds the main mill structure; the eastern side preserves the poorly surviving outlines of associated buildings. Neither is in good condition, and the vegetation has advanced considerably, but the earthwork traces of the millrace give a useful sense of how the water was managed and how the site was organised around it.