[Illustration: Portion of the Chain Stretched Across the Entrance of the Golden Horn in 1453.] The employment of a chain to bar the entrance of the Golden Horn is mentioned for the first time in the famous siege of the city by the Saracens in 717-718, when the Emperor Leo lowered the chain with the hope of tempting the enemy’s ships into the narrow waters of the harbour.[833] It appears next in the reign of Michael II., who thereby endeavoured, but in vain, to keep out the fleet with which his rival Thomas attacked the city.[834] It was again employed by Nicephorus Phocas, in expectation of a Russian descent into the Bosporus.[835] The Venetians found it obstructing their path when they stood before Constantinople in 1203, but removed it after capturing the Tower of Galata, to which it was secured.[836] Finally, in 1453, it proved too strong for Sultan Mehemet to force, and drove him to devise the expedient of carrying his ships into the Golden Horn across the hills to Cassim Pasha.[837] A portion of the chain used on the last occasion is preserved in the Church of St. Irene, within the Seraglio grounds. In the district of Eugenius were some of the most noted charitable institutions of the city, among which the great Orphanage[838] and the Hospitia,[839] built on the site of the old Stadium of Byzantium by Justinian the Great and Theodora, for the free accommodation of poor strangers, were conspicuous. There, also, stood the Church of St. Michael and the Church of St. Paul.[840] The Basilikè Pylè. Before concluding the study of the Harbour Walls we must recur to the question which presented itself at an earlier stage of our inquiries, but was reserved for consideration at the close of this chapter, as more favourable to an intelligent and thorough discussion of the subject. Where was the Basilikè Pylè which Byzantine historians, after the Restoration of the Empire, associate with this line of the city’s bulwarks? Was it, as some authorities maintain, at Balat Kapoussi,[841] or, as others hold, in the neighbourhood of the Seraglio Point?[842] Or is it possible that a gate bearing that epithet was found at both points? In favour of the opinion that the Imperial Gate was near the Seraglio Point there is, first, the statement of Phrantzes, already cited, to that effect. “To Gabriel of Treviso,” says the historian,[843] “captain of the Venetian triremes, with fifty men under him, was entrusted the defence of the tower, in the middle of the current, guarding the entrance of the harbour; and he was opposite the Imperial Gate.”