The photos below were taken by me in 2003 of a Souterrain beside the Cushendall Rd at Drumnakeel near Ballycastle in North Antrim.
The Entrance from the corridor to the refuge.
Inside the Souterrain
Entrance from outside
Souterrains are often referred to locally in Ireland simply as ‘caves’. A. T. Lucas, a folklorist and Director of the National Museum of Ireland in the 1960s, published a series of articles on the references to souterrains in the early Irish annals. Donaghmore Souterrain, discovered in County Louth in 1960, and Drumlohan Souterrain, County Waterford are the only souterrains to be an Irish National Monument.
In Ireland souterrains are often 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. Their distribution is very uneven in Ireland with the greatest concentrations occurring in North Louth, North Antrim, Sligo, 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.
An article by Warner on the archaeology of souterrains, although published 38 years ago, is still possibly the best general overview of the subject.
The most comprehensive study of Irish souterrains is M. Clinton’s 2001 work, containing chapters on distribution, associated settlements, function, finds, chronology and no less than thirteen appendices on various structural aspects of souterrains themselves.
 Ref: Archeology Ireland Magazine 2017