Lime kilns were once as common across rural Ireland as stone walls, built to produce quicklime by burning limestone at intense heat, typically in a stone-lined bowl or draw kiln. The resulting material was essential to pre-modern farming, spread across acidic fields to sweeten the soil, and used in the making of mortar for local buildings. That so many survive at all is partly because they were built to last, and partly because nobody thought them worth demolishing.