The church occupies the highest point of an ancient circular mound that rises 3 metres above the surrounding grazing land, measuring 45 metres north to south and 38 metres east to west. Today, this elevated site serves as a graveyard containing over 200 marked burials dating from 1735 to 1983, enclosed by a rubble stone wall that follows the mound’s contours.

Historical records first mention Tullaghobegly in a 1622 Royal Commission report, which already described it as being ‘in ruins’, suggesting the church had been abandoned well before the 17th century. Archaeological evidence points to its original construction in the 13th century, with a square tower likely added to the southwest end during the 15th century. Of the original structure, only a section of the north wall and part of the east gable survive, standing up to 3 metres high. The most notable architectural feature is a two period window in the east gable; the earlier window had a round headed, narrow opening with traces of plaster still visible on its soffit, whilst a later modification partially blocked this original opening.

Excavations carried out in 1992 revealed the church’s full footprint and uncovered an intriguing collection of artefacts beneath centuries of accumulated earth. Alongside numerous burials and disarticulated bones, archaeologists found 267 clay pipes dating from 1870 to 1910, over a hundred 19th and 20th century bottles, coins including a counterfeit 1783 halfpenny, and even a .303 bullet shell from the Second World War era. The dig also confirmed the presence of the tower foundations, with walls measuring up to 1.25 metres wide; substantially thicker than those of the main church to support the weight of the vertical structure. From its commanding position, the site offers panoramic views stretching from the Atlantic coast to the dramatic peaks of Errigal, Muckish and Aghla Mór, making it easy to understand why this spot was chosen for a place of worship all those centuries ago.