The largest of the three rooms measures less than two metres in length and barely over a metre wide. To move between them, a person would have had to crawl.

This is a souterrain, a type of underground structure found widely across early medieval Ireland, typically associated with ringforts and farmsteads. The word is borrowed from the French for "underground passage", and while the exact function of these structures is still debated, they are generally thought to have served as cool storage spaces, places of refuge, or both. The Inchincurka example was discovered in 1956, and was described by McCarthy in 1977 as consisting of at least three earth-cut chambers arranged in a roughly north-east to south-west line, each connected to the next by a creephole, a low, narrow opening just wide enough to squeeze through. Two of the chambers, the second and third, contain a particular feature worth noting: short recessed stone walls with pits set behind them, possibly used for storing perishables or concealing valuables. The first chamber is the smallest, at one and a half metres long and only seventy-five centimetres high, a space in which even crouching would be difficult.