Akbıyık Sultan (real name Ahmed Şemseddin) was a Bayrami-minded dervish, one of the leading disciples of Hacı Bayram-ı Veli. He was among the warrior-shaykhs who joined the 1444 Varna campaign and the 1453 conquest of Istanbul. After the conquest a mosque bearing his name arose near Hagia Sophia, in today's Ahırkapı-Cankurtaran quarter, which came to be called after him. He spent his final years in Bursa in remembrance, worship and teaching. He died in 860/1456 and his actual tomb is in his own complex near Bursa's Grand Mosque. In the courtyard of the Akbıyık Mosque in Istanbul there is only a symbolic cenotaph in his name, bearing a stone dated 894/1488-89; the Istanbul site is therefore recorded with the transparency note "maqam — actual grave in Bursa."