The evidence is plain in the masonry: one section is neatly coursed and symmetrical, the other rougher and irregular, the two parts meeting at a slight misalignment that archaeologists read like a seam. What makes this particular souterrain, a roofed underground passage associated with early medieval ringforts and used variously for storage, refuge, or ventilation, especially notable is not its size but its engineering. Running off the southern end of the main tunnel was a ventilation shaft, barely 25 centimetres wide internally, that Seán P. Ó Ríordáin judged the finest example of such a feature found across any of the Cush souterrains.

Ó Ríordáin excavated the site between 1934 and 1935, publishing his findings in 1940. The souterrain sits in the southern quadrant of a bivallate ringfort, meaning a roughly circular farmstead enclosure defined by two concentric earthen banks, at Cush in County Limerick. A second souterrain was also uncovered in the northern quadrant of the same ringfort. The southern example measured ten metres in length and between 0.9 and 1.5 metres in width, narrower in its older, more carefully built southern section and broader where the later, less accomplished addition joined it. The ventilation passage extended a further 4.9 metres from the end wall, entering the souterrain at a height of 1.5 metres above the floor, with some of the flat covering slabs still in place at the time of excavation.

There is nothing to see above ground today. Satellite imagery taken between 2011 and 2013 shows no surface trace of either the ringfort or its souterrains, and more recent aerial photography confirms the same absence. For anyone with a particular interest in early medieval archaeology, the significance of Cush lies in the published record rather than any visible monument. Ó Ríordáin's 1940 report, with its plans and descriptions, remains the primary document, and the site is recorded under the Sites and Monuments Register reference LI048-034037. The landscape around Cush is otherwise unremarkable farmland, which makes the density of early medieval activity once concentrated here all the more quietly arresting.