The ogee-headed windows in the nave of this ruined medieval church on the edge of Straffan village are, by all appearances, in the wrong places. Whoever reassembled them during a later phase of rebuilding seems to have misread the originals, leaving behind a small architectural puzzle embedded in the limestone walls. An ogee window, recognisable by its double-curved pointed arch, was a fairly refined decorative feature for a modest parish church, and the fact that these ones survive at all, however awkwardly repositioned, gives the ruin an odd, slightly off-kilter quality that rewards a close look.

St. Patrick's of Straffan has a long and episodic history. Around 1250, according to the historian Ronan, it was incorporated into the Hospital of St. John by a man named Robert de Capella. By 1531, the vicarage had been restored by Alen, reportedly at considerable effort and cost. A visitation in 1615 found both the church and chancel in good repair, but only fifteen years later, in 1630, things had deteriorated sharply: a contemporary account recorded that 'the body of the church is ruinous; the chancel is well covered, but wants Glassinge and necessary ornaments.' That distinction between a failing nave and a still-functioning chancel is written into the fabric of the building even now. The chancel walls are noticeably thicker and more substantial than those of the nave, and the two sections are not bonded to one another at the dividing wall, suggesting the chancel may actually be the older or separately constructed portion. Attached to the west end of the church is a four-storey rectangular tower with a double bellcote on its east wall, the whole structure built from randomly coursed, roughly dressed limestone. Later buttresses were added at the north and south to stabilise the junction between tower and church, and several openings throughout, including a doorway into the tower, are now blocked.