Sitting roughly a mile north-west of the present town of Kilmallock in County Limerick, this small rectangular ruin is dedicated to St. Mocheallog, the early medieval saint from whom the town itself takes its name. By 1840 the walls stood only a couple of feet high, and by the early twentieth century they were described as nearly covered with earth and grass, the large dry-stone blocks, laid without lime mortar, barely distinguishable from the rising ground around them.

The building was modest even in its prime, measuring roughly 6.8 metres long and 3.7 metres wide, with walls about 0.9 metres thick. Dry-stone construction of this kind, where large blocks are fitted without binding mortar, is characteristic of early ecclesiastical buildings in Ireland and points to considerable age. St. Mocheallog himself died somewhere between 639 and 656 AD, and his feast day falls on the 26th of March. The site appears in the historical record with some vividness: in 1318, a man named Nic. Kerdiff sought sanctuary here, the plea rolls recording that he had fled to the church of St. Myhallok at Kylmehalloc. By 1410, the church was being noted in written sources as situated on the hill of Kilmallock, suggesting it retained some significance well into the medieval period. The antiquarian Thomas Johnson Westropp recorded its dimensions and fabric in the early twentieth century, and Begley's 1906 account of the diocese preserves the most detailed physical description that survives.

The site sits in the northern quadrant of a rectangular graveyard that is, by all accounts, now scarcely used. Aerial photographs confirm the footprint is still traceable, though anyone visiting should expect very little to be visible above ground level; the archaeology here is largely a matter of knowing where to look and understanding what the slight undulations in the grass represent. The graveyard itself provides the clearest orientation point. Given the low-lying nature of the remains, a visit in late winter or early spring, when vegetation is thin, offers the best chance of making out the wall line. The 26th of March, St. Mocheallog's feast day, has its own quiet resonance as a date to visit a place that has otherwise slipped almost entirely from view.