In 1550 the town and friary were burned by O'Carroll.
There are still a few fragments of the Dominican friary founded in 1269.
Of the old castle, called Nenagh Round, dating from the time of King John, there still exists the circular donjon or keep. There are no remains of the hospital founded in 1200 for Austin canons, nor of the Franciscan friary, founded in the reign of Henry III.
During the next two centuries the councils devoted much attention to heresy: eight propositions concerning the body of Christ after his death were rejected at St Mary-le-Bow in 1286; the expulsion of the Jews from England was sanctioned by a legatine synod of Westminster in 1291; ten theses of Wiclif's were condemned at the Dominican friary in 1382, and eighteen articles drawn from his Trialogus met the same fate at.