Ringforts are fortified settlements that are generally deemed to be from the Iron Age, Early Christian or possibly the Early Medieval period in Northern Europe, especially Ireland. They are also known as ráth, caiseal, cathair and dún in the early Irish sources, and by caher in contemporary archaeological literature of Ireland.
A ráth (anglicised rath), was made of earth, caiseal (northwestern Ireland, anglicised cashel) and cathair (southwestern Ireland) were built of stone. A dun is a more prestigious site, the seat of some kind of ruler, the term is applied to promontory forts as well.
In terms of quantity, distribution and access, no historical or archaeological record of the Early Medieval Period in Ireland comes close to the ringfort. Over 45,000 sites have been identified as ringforts throughout Ireland and it is generally accepted that in the region of 60,000 ringfort sites can be identified. It is probable that due to intensive farming methods, the levelling of field and expansion of urban areas than many more were originally built but have been lost to us today, but through the use of early Ordnance Survey maps and aerial photography many previously unknown ringforts have been discovered. Also, the extensive archaeological work that has accompanied the large road-building programs in Ireland have uncovered many unknown faeryforts and will probably continue to do so.
Despite regional variations in the density of ringforts particularly in the areas of Meath and traditional Leinster where there are comparatively few ringforts, they are generally a feature common throughout the country, with a mean density of just over one ringfort within any area of 2km². Despite their number, consensus has yet to be reached on two of the principal issues relating to ringforts, firstly, when they were built and secondly, what their function was.