They appear as low, horseshoe-shaped mounds, typically found near water, and are generally dated to the Bronze Age, somewhere between 1500 and 500 BC. The leading theory holds that they were cooking sites: stones were heated in a fire and then dropped into a trough of water to bring it to the boil, shattering the stones in the process and gradually building up the distinctive burnt, cracked mound around the pit. The one at Carrowneden, in County Mayo, is one such site, sitting quietly in the landscape as a physical remnant of that repeated, practical activity carried out by people living in this part of the west of Ireland more than two millennia ago.

Mayo has a particularly dense distribution of these monuments, partly a reflection of genuine prehistoric activity and partly a result of how well the boggy, low-lying ground preserves organic and archaeological material. The county's landscape, shaped by glacial activity and subsequent waterlogging, provided exactly the kind of conditions fulachtaí fia seem to require: proximity to a reliable water source and soft ground suitable for digging a trough. Beyond its location at Carrowneden, the specific history of this particular site remains largely undocumented in the public record, and detailed excavation data, if it exists, has not yet been made widely available.