The pointed arch, dating to around the fifteenth century, is cut from chamfered limestone, meaning the stone edges have been bevelled at an angle to give a clean, slightly decorative profile, and it terminates in what is called a plain stop, where the moulding simply ends flat against the wall. It is a survivor from an entirely different building, absorbed quietly into a much later structure, and most people walking through it would never think to look up.

The church of St Patrick, built in 1758, stands on ground that has been used for Christian worship for considerably longer. A reference recorded by Walsh in 1888 notes that by 1275 there was already a monastery of Grey Friars on or near this site. The Grey Friars were Franciscans, a mendicant order who typically built in towns and relied on alms rather than land revenues, so their presence here points to a community of some significance in medieval Donabate. By the time of the Civil Survey of 1654 to 1656, that earlier religious life had been reduced to walls, the survey recording simply the remains of a parish church. When the antiquarian D'Alton visited in 1838, some of those older remnants were still visible alongside the Georgian building that had replaced them, though what precisely he saw is not recorded in detail. The medieval doorway, however, was preserved deliberately, set into the new porch as the entrance through which the congregation would pass.

The church is in Donabate village, north County Dublin, and is a Church of Ireland parish church still in use. The medieval doorway is in the porch, so it is most easily examined on the way in or out during an open service, or if the building happens to be unlocked. It is worth pausing at the arch itself and looking at the stonework closely, the chamfering and the stop are subtle features but they are the clearest surviving evidence of a religious presence on this site stretching back at least to the thirteenth century.