A notable example of fortified Norman architecture, King John's Castle was built between 1200 and 1216, and guards Thomond Bridge on the east bank of the River Shannon. It has no keep. However, massive round towers reinforce the gate and the curtain walls, which used to be higher, for they were built to withstand the siege machines of the time. The castle was extensively repaired in 1216, and features often in Irish annals as an important stronghold.