The catch is that nobody can see it. There is no hollow in the ground, no protruding stonework, no depression in the grass to betray its presence. It has, for all practical purposes, vanished beneath the surface.

What is known comes from a single observation made in 1939 by P. J. Hartnett, who recorded what he described as what appears to be a cave site, slightly to the West of centre, within the bounds of a cashel. A cashel is a stone-walled enclosure, roughly circular, used as a farmstead or defensive enclosure during the early medieval period, and the one at Lyroe provides the broader context for the souterrain beneath it. Souterrains and cashels frequently occur together across Munster, the underground structure typically associated with the settlement that the cashel enclosed. Hartnett's wording is cautious, and deliberately so; even in 1939 the evidence was ambiguous enough that he stopped short of a firm identification. Since then, no visible surface trace has been recorded.