In Ireland, souterrains often are found inside or in close proximity to a ringfort and as such are thought to be mainly contemporary with them, making them somewhat later in date than in other countries. This date is reinforced by many examples where ogham stones dating to around the 6th century have been reused as roofing lintels or door posts, most notably at the widened natural limestone fissure at the ‘Cave of the Cats’ in Rathcrogan. The distribution of souterrains is very uneven in Ireland, with the greatest concentrations occurring in north Louth, north Antrim, south Galway, and west Cork and Kerry. Lesser numbers are found in counties Meath, Westmeath, Mayo, north Donegal, and Waterford. Other counties, such as Limerick, Carlow, and Wexford, are almost completely lacking in examples.