These features, known to archaeologists as burnt mounds, or fulachtaí fia in Irish, are among the most common ancient monument types in Ireland, yet they remain poorly understood. The working theory is that people heated stones in a fire, dropped them into a water-filled trough to bring it rapidly to the boil, and used the result for cooking, bathing, or some kind of craft process such as working leather or brewing. The spent, fractured stones were then raked aside, building up over time into the distinctive horseshoe or kidney-shaped mound that survives today.

Burnt mounds of this kind date broadly to the Bronze Age, roughly 2000 to 500 BC, though some examples fall outside that range. They tend to cluster near reliable sources of water, since the whole process depended on a ready supply, and Six-Mile-Bridge sits on the River Owenogney close to its confluence with the River Shannon, making the surrounding ground well suited to exactly that kind of repeated, water-dependent activity. The village itself takes its name from its distance along an old road, and the area has been a crossing point and a place of settlement for a very long time. The burnt mound is a reminder that this particular patch of Clare was well used long before any bridge was built or any mile was measured.