After the fall of paganism, Hieron had many vicissitudes. Having been converted into one of the strongest fortresses on the Bosphorus, it was time and again singled out for attack by the enemies of the Byzantine Empire. Among the most celebrated of them was Harun-al-Rashid who led an army the whole way from Bagdad with a view of effecting the conquest of Constantinople and with it of the Byzantine Empire. At a later date Hieron and the stronghold on the opposite side of the Strait fell into the hands of the Genoese. Not long afterwards it was captured by the Sultan Bayazid I, “the Thunderbolt,” and since then it has been in the possession of the Turks. A short distance to the southwest, on the European shore, is a beautiful valley where the Crusaders are said to have encamped on their way to the Holy Land. A colossal plane tree is here seen which bears the name of “Plane tree of Godfrey of Bouillon,” from a tradition that it was planted by this famous hero of the Christian host. At Roumeli Hissar, we reach the narrowest point of the Bosphorus and one which is most rich in historical associations. According to tradition, it was here that Xenophon and his immortal Ten Thousand crossed over into Europe after their famous retreat from the heart of Babylonia--a retreat which, revealing, as it did, the military weakness of the Persian Colossus, paved the way for the victories of the Granicus, the Issus, and Arbela and for the conquest of Asia by Alexander the Great. Here, too, it was that Mandrocles of Samos constructed the bridge of boats that enabled the vast Persian army under Darius to cross into Europe at the time of that monarch’s disastrous campaign against the Scythians. Mandrocles was so elated by his achievement that he had it commemorated in the temple of Hera, in his native Samos, by a picture with the inscription: _The fish-fraught Bosphorus bridged, to Juno’s fane_ _Did Mandrocles this proud memorial bring;_ _When for himself a crown he’d skill to gain,_ _For Samos praise, contenting the Great King._