These are fulachta fia, a type of prehistoric burnt mound found widely across Ireland, typically consisting of a horseshoe-shaped heap of fire-cracked stone and charcoal accumulated around a trough where water was once heated by dropping in stones from a fire. At Coan, not one of the five leaves any trace above the surface, which gives the cluster a quietly unsettling quality: a busy prehistoric landscape, preserved only in the soil.

The five sites sit on a terrace to the north of the Dinin river valley and along the western side of a small stream valley, and were identified by Prendergast in 1977. What draws particular attention is their proximity to a spring well. Fulachta fia are almost always found near water, since the whole process depended on a reliable supply, and the presence of a natural spring here may well explain why this particular terrace attracted repeated use. Five sites clustered together in one area suggests not a single episode of activity but something more sustained, perhaps a location returned to across generations during the Bronze Age, when fulachta fia were most commonly in use.