Darius commanded Mandrocles to build a bridge over the Bosphorus, which lay in the direction of his march. This strait was narrower than the Hellespont, but the current which sets through it from north to south was much stronger. Mandrocles began the structure with the crews and materials of the fleet which had been ordered to assemble.[256] Several hundreds of ships, fastened together, were placed in the strait,[257] and carefully anchored against the north wind and the current. On the coast of Asia, the bridge lay to the north of the city of Chalcedon and in its territory; Herodotus supposes that the European end touched the shore between Byzantium and the temple, which, situated to the north of Byzantium at the mouth of the Pontus, served as a signal to the ships entering the Bosphorus.[258] Polybius remarks that the bridge "was said" to end at the Hermaeum, which lay on the promontory of the European shore.[259] Strabo places this temple ten stadia to the south of the northern entrance of the Bosphorus.[260] Hence we may assume that Mandrocles constructed his bridge across the narrowest part of the strait, about 1000 paces in breadth,[261] and that it lay at the place where the castles of Anadoli Hissari and Rumili Hissari now stand opposite each other. The army was collected, the bridge was ready, when Darius came to Chalcedon. He inspected the bridge, and was greatly pleased with the construction; he embarked on board ship and proceeded for some distance into the Pontus, then he returned to the temple of Zeus Urius on the shore of Asia, at the mouth of the Bosphorus, and looked out into the sea. Before his wishes and his power, and the skill of his Greek engineer, the impossible had become possible; the Bosphorus was compelled to submit to a bridge. Mandrocles received the most valuable presents. The fleet of the Ionians lay on the Black Sea, when the army, which was the greatest that a Persian sovereign had ever brought together, commenced the passage. The train was interminable which filed before the king over the sea; the rock on which Darius sat was pointed out for a long time afterwards. Even "shepherd Sacæ, of the race of the Scythians, the children of a nomad race," passed over the bridge;[262] the nomads of the steppes of the Oxus were led by Darius against the nomads of the steppes to the north of the Pontus. In remembrance of this passage Darius caused two columns of white stone to be erected on the European shore, which recorded the names of all the nations included in the army; the inscription on one side was in the Persian cuneiform (in Assyrian letters, as Herodotus says), and on the other in the Hellenic language and letters. Mandrocles also was proud of his work, and dedicated a picture which represented the bridge, the army crossing it, and Darius sitting on his throne, in the great sanctuary of his city, the temple of Hera at Samos, with the following inscription: "When