Old St Mary's Church is Clonmel's most atmospheric medieval survival, a parish church whose grounds still show the defensive edge of the old town. The walls, tower, grave markers, and layered stonework give a better sense of Clonmel's age than the busier commercial streets nearby.
It is a small sight, but a worthwhile one if you are walking the historic centre. Pair it with the Main Guard and the quays to understand how the town grew around river trade, religion, and fortification. The churchyard is often the most evocative part.