It does not appear on Ordnance Survey maps. The only signs that anything lies beneath are two ragged openings in the earth, roughly 3.6 metres apart, where roofing slabs have given way and dropped into the void below.

A souterrain is a man-made underground passage or chamber, typically built during the early medieval period in Ireland as a place of refuge or storage, and sometimes connected to a nearby settlement. The Letternadarriv example was constructed with a lintelled passage, meaning flat slabs were laid across the top to form a roof, supported by earthen sides rather than stone walling. It runs east to west before curving south-east, and where it can still be glimpsed through the collapse openings, the passage measures around 0.8 metres wide and up to 0.6 metres high, a space more suited to crawling than walking. Both ends are now entirely blocked by fallen material, and the interior has flooded, leaving the full extent of the structure unknown. Its position on a rise in otherwise boggy ground, on the eastern side of the river valley, would have made it a relatively dry and defensible spot when it was originally built, though it sits now in an area that clearly tests the patience of the surrounding land.

The fencing around the site is there for good reason. The ground above a collapsed souterrain is unpredictable, and the combination of waterlogging and structural failure makes this one to observe from a careful distance rather than to investigate closely.