They appear as low, horseshoe-shaped mounds, typically found beside streams or marshy ground, and are thought to date largely from the Bronze Age. One such site sits quietly in the townland of Callow in County Mayo, its mound a remnant of activity that took place perhaps three or four thousand years ago.

The prevailing interpretation of fulachtaí fia is that they functioned as outdoor cooking sites. The method was straightforward: stones were heated in a fire, then dropped into a water-filled trough, bringing the water rapidly to a boil. The cracked and shattered stones, rendered useless by repeated heating, were discarded to the sides of the trough, and it is these accumulations of fire-broken rock that form the characteristic mounds still visible today. Some researchers have proposed alternative uses, including textile processing or even bathing, though cooking remains the most widely accepted explanation. Mayo, with its abundance of low-lying wet ground, is particularly rich in these sites, and the Callow example is one of many that punctuate the county's boggy interior.

Because the available documentation for this particular site is limited, specific details about its dimensions, condition, or precise location within the townland cannot be confirmed here. What can be said is that Callow, like many Mayo townlands, is a quietly archaeological landscape, where Bronze Age remains often survive beneath or alongside bog and pasture with little to mark them out from the surrounding ground.