The final slaughter of the Christians occurred at this location.  But the Ottomans broke through the outer wall at San Romano gate.

Fall of Constantinople

The Fall of Constantinople (Turkish: İstanbul'un Fethi; Greek: Άλωση της Κωνσταντινούπολης, Alōsē tēs Kōnstantinoupolēs) was the capture of Constantinople, the capital of the Byzantine Empire, which occurred after a siege by the Ottoman Empire, under the command of 21-year-old Ottoman Sultan Mehmed II, against the defending army commanded by Byzantine Emperor Constantine XI Palaiologos. The siege lasted from Friday, 6 April 1453 until Tuesday, 29 May 1453 (according to the Julian calendar), when the city was conquered by the Ottomans.

• http://en.wikipedia.org/wiki/Fall of Constantinople
• Spilling, M., 2010, Battles that Changed History: Key Battles that Decided the Fate of Nations: Amber Books, London, 448p