They appear as low, horseshoe-shaped mounds of fire-cracked stone and dark, charred soil, the physical residue of an ancient cooking method in which stones were heated in a fire and then dropped into a water-filled trough to bring it rapidly to the boil. The example at Fanygalvan in County Clare is a particularly well-preserved specimen of the type, sitting on level ground within a large field system that shows signs of activity across multiple periods of prehistory.

The mound itself is subcircular in plan, measuring roughly 14 metres east to west and 11.5 metres north to south, and rising to between 1.2 and 2 metres in height. Its summit is notably flat, spanning about 4.5 metres across, and the whole structure is grass-covered, with the characteristic dark soil and burnt stone visible beneath. Two disturbed arms extend northward from the main body, each roughly 1.1 to 1.7 metres wide, curving inward to enclose an oval space of approximately 4 metres by 4 metres that sits slightly higher than the surrounding ground. At the northern edge of the monument, a ring of stones some 4.8 metres in diameter protrudes through the turf, most likely indicating the top of a stone-lined trough where the actual heating and boiling of water would have taken place. Around 10 metres to the northeast, a well still in use for cattle provides a reminder that the logic of the site, water close at hand, has remained constant across the centuries. Nearby hut sites lie to the south and south-southwest, suggesting this was once part of a more extensive settlement or working landscape rather than an isolated feature.

The Fanygalvan fulacht fia sits within a broader multiperiod field system, which gives the site an added layer of interest. What looks from a distance like an unremarkable grassy mound at the edge of farmland is, on closer inspection, one component of an ancient organised landscape, where people lived, worked, cooked, and managed the land across generations whose precise chronology remains difficult to pin down.