But though the seaward walls did not possess the military consequence of the land walls, they are interesting on account of their connection with important political events, and, above all, for their intimate association with the commercial activity of the greatest emporium of trade during the Middle Ages. The history of the construction of these walls has already been noticed incidentally, when tracing the gradual expansion of the city.[621] In the days of Byzantium they proceeded, we have seen, from the Acropolis (Seraglio Point) to the Neorium, on the Golden Horn; and to the point subsequently called Topi, on the Sea of Marmora. Under Constantine the Great they were carried to the Church of St. Antony Harmatius, on the northern side of the city; and to the Church of St. Æmilianus, on the southern. In 439, Theodosius II. prolonged the lines to meet the extremities of the land wall at Blachernæ, on the one hand, and the Golden Gate, on the other. The history of the repair of these walls from time to time is a long one. For while comparatively secure from injury by the accidents of war, they were liable to be rudely shaken by earthquakes, like other public buildings of the city, while their proximity to the sea exposed them in a special manner to damage by damp and storm. During the earlier days of the Empire, indeed, when the Imperial navy ruled the sea, and no hostile fleet dared approach the city, the condition of these fortifications was often neglected; but as the sea-power of the Empire decayed, and that of other nations grew stronger, the defences along the shores of the city assumed greater interest, and their maintenance in proper order became one of the principal cares of the State. The earthquake of 447, so ruinous to the new land wall of Anthemius, injured also the seaward walls, especially the portion beside the Sea of Marmora. As an inscription over Yeni Kapou[622]—the gate at the eastern end of Vlanga Bostan—proclaimed, the damage was repaired by the Prefect Constantine when he restored the other fortifications of the city which had suffered from that terrible earthquake.[623] There is no record of repairs for the next two hundred and fifty years. But the state of these walls could not have been altogether unsatisfactory during that period, for they were prepared to withstand two fleets which threatened the southern side of the city in the seventh century: first, when the ships of Heraclius came, in 610, to overthrow the tyranny of the infamous Phocas; and again, when the Saracens besieged Constantinople from 673-678.