قسطنطين الحادي عشر
The Gate of St. Romanus () was named so after a nearby church and lies between towers 65 and 66. It is known in Turkish as "Topkapı", the "Cannon Gate", after the great Ottoman cannon, the "Basilic", that was placed opposite it during the 1453 siege. With a gatehouse of 26.5 m, it is the second-largest gate after the Golden Gate. According to conventional wisdom, it is here that Constantine XI Palaiologos, the last Byzantine emperor, was killed on 29 May 1453.