There's a legend that during the Fall of Constantinople in 1453 an angel of the Lord had rescued the emperor Constantine XI when he was about to be killed by the Turks. The angel had swept him up, turned him into marble and concealed him in a subterranean cave near the Golden Gate of the city. There the marble emperor sleeps and awaits the angel's call to wake up. The Turks, continues the legend, know all about this miracle, but they cannot find the cave. So, they have walled up the Golden Gate through which the emperor will one day come to liberate the city. But when God so wills the angel will come down, reanimate the marble emperor and give him back the sword which he had in the battle; and he will come to life, march into the city and chase the Turks as far as Red Apple Tree.
In 1625 Sir Thomas Roe, then British ambassador to the Porte, sought permission to remove some of the antique statuary and carved stones from above the Golden Gate to send them to the Duke of Buckingham for his collection of antiquities. He observed that the Golden Gate had been walled up and had never been opened since 'the Greek Emperors' lost the city. He failed to remove them not so much because of official interference as of local opposition. The Turks round about had a superstitious dread of the Golden Gate and all that went with it. Sir Thomas's interpreter told him that there was a prophecy that the statues on it were enchanted and that if they were taken down 'some great altercation should befall this city. He spake of a vault underground, that I understand not;...and it is true that, though I could not get the stones, yet I almost raised an insurrection in that part of the citty.'
Source: The Immortal Emperor: The Life and Legend of Constantine Palaiologos, Last Emperor of the Romans by Donald M. Nicol