Yet the very difficulty of reading the ruin is part of what makes it interesting. When antiquarians examined the site in 1839, they noted that all architectural features had already been destroyed, leaving the character of the masonry itself as the only guide to age. That masonry is cyclopean, meaning it is built from unusually large, irregular blocks, and both early observers and later researchers concluded it pointed to considerable antiquity.

The church appears in the Papal Taxation lists of 1302 under the name Kilmugown, which gives it a firm medieval documentary footing, but the structure itself is thought to be considerably older. It was dedicated, according to a suggestion made in 1839, to St Múdhain, also rendered Muadanus or Mudanus, and the antiquarian T. J. Westropp, writing at the turn of the twentieth century, proposed that the founder may have been a figure called Mogua. Westropp also recorded something now lost: a pier and corbel belonging to an arched canopy over the altar, visible within the rubble-filled interior when he visited. A plinth he noted on the east gable has since disappeared as well. The church is roughly 18.7 metres long and 6.9 metres wide, and its north wall is built into the boundary of the surrounding graveyard, effectively doubling as the graveyard's own north perimeter. Immediately to the south, and almost touching it, stands a medieval house. The wider landscape adds further layers: a holy well lies roughly 157 metres to the west-southwest, and a standing stone, now fallen, once stood about 470 metres to the east-northeast. That stone may have served as a termon marker, a boundary stone demarcating the sanctuary land associated with the church, a practice known from other early Irish ecclesiastical sites.