The walls rise to no more than 2.5 metres at their highest, the east end is entirely gone, and the rectangular doorway near the western end of the south wall is made of roughly shaped stone rather than anything finely dressed. What survives, in other words, is fragmentary, but the fragments are suggestive of a building that was once organised and purposeful, set within a subcircular enclosure on the western shore of Lough Owel in County Westmeath.

The site takes its name from Lomán, son of Oireannan, a saint associated with this stretch of the lough and with a second church on Church Island, known in Irish as Inis Mór, further out on the water. His feast day fell on either the 7th or the 3rd of February, the uncertainty itself a small reminder of how lightly the early medieval church trod across the historical record. The church at Portloman, also referred to in older sources as Teach Lomáin or possibly Teach Mic Luim, stood on the Slighe Asail, one of the ancient roads that crossed Ireland in the early medieval period. Local tradition held that the Amhra, a sacred song associated with Colum Cille, was sung along a penitential route connecting the church to a stone cross that still stands some six metres to the west of the ruin, and to a station called Leac Lomán, located roughly 800 metres to the south-west. A cross-inscribed stone shaped like a coffin lid was unearthed from the clay at some point before 1876, when the ruins were measured at roughly 23.5 metres long by 6.2 metres wide; it was thought at the time to mark the grave of an ecclesiastic. A bowl-barrow, a low circular burial mound of likely prehistoric origin, lies 230 metres to the west, a quiet indication that the ground here carried significance long before Lomán's church was built.