But the history of Constantinople cannot be understood unless the extraordinary character of the geographical position of the place is present to the mind. No city owes so much to its site. The vitality and power of Constantinople are rooted in a unique location. Nowhere is the influence of geography upon history more strikingly marked. Here, to a degree that is marvellous, the possibilities of the freest and widest intercourse blend with the possibilities of complete isolation. No city can be more in the world and out of the world. It is the meeting-point of some of the most important highways on the globe, whether by sea or land; the centre around which diverse, vast, and wealthy countries lie within easy reach, inviting intimate commercial relations, and permitting extended political control. Here the peninsula of Asia Minor, stretching like a bridge across the seas that sunder Asia and Europe, narrows the waters between the two great continents to a stream only half a mile across. Hither the Mediterranean ascends, through the avenues of the Ægean and the Marmora, from the regions of the south; while the Euxine and the Azoff spread a pathway to the regions of the north. Here is a harbour within which the largest and richest fleets can find a perfect shelter.
But no less remarkable is the facility with which the great world, so near at hand, can be excluded. Access to this point by sea is possible only through the straits of the Hellespont on the one side, and through the straits of the Bosporus on the other—defiles which, when properly guarded, no hostile navy could penetrate. These channels, with the Sea of Marmora between them, formed, moreover, a natural moat which prevented an Asiatic foe from coming within striking distance of the city; while the narrow breadth of the promontory on which the city stands allowed the erection of fortifications, along the west, which could be held against immense armies by a comparatively small force.
As Dean Stanley, alluding to the selection of this site for the new capital of the Empire, has observed: “Of all the events of Constantine’s life, this choice is the most convincing and enduring proof of his real genius.”
Although it does not fall within the scope of this work to discuss the topography of Byzantium before the time of Constantine, it will not be inappropriate to glance at the circuits of the fortifications which successively brought more and more of this historic promontory within their widening compass, until the stronghold of a small band of colonists from Megara became the most splendid city and the mightiest bulwark of the Roman world.
Four such circuits demand notice.
First came the fortifications which constituted the Acropolis of Byzantium.[[4]] They are represented by the walls, partly Byzantine and partly Turkish, which cling to the steep sides of the Seraglio plateau at the eastern extremity of the First Hill, and support the Imperial Museum, the Kiosk of Sultan Abdul Medjid, and the Imperial Kitchens.
That the Acropolis occupied this point may be inferred from the natural fitness of the rocky eminence at the head of the promontory to form the kind of stronghold around which ancient cities gathered as their nucleus. And this inference is confirmed by the allusions to the Acropolis in Xenophon’s graphic account of the visit of the Ten Thousand to Byzantium, on their return from Persia. According to the historian, when those troops, after their expulsion from the city, forced their way back through the western gates, Anaxibius, the Spartan commander of the place, found himself obliged to seek refuge in the Acropolis from the fury of the intruders. The soldiers of Xenophon had, however, cut off all access to the fortress from within the city, so that Anaxibius was compelled to reach it by taking a fishing-boat in the harbour, and rowing round the head of the promontory to the side of the city opposite Chalcedon. From that point also he sent to Chalcedon for reinforcements.[[5]] These movements imply that the Acropolis was near the eastern end of the promontory.
In further support of this conclusion, it may be added that during the excavations made in 1871 for the construction of the Roumelian railroad, an ancient wall was unearthed at a short distance south of Seraglio Point. It ran from east to west, and was built of blocks measuring, in some cases, 7 feet in length, 3 feet 9 inches in width, and over 2 feet in thickness.[[6]] Judging from its position and character, the wall formed part of the fortifications around the Acropolis.
The second circuit of walls around Byzantium is that described by the Anonymus of the eleventh century and his follower Codinus.[[7]] Starting from the Tower of the Acropolis at the apex of the promontory, the wall proceeded along the Golden Horn as far west as the Tower of Eugenius, which must have stood beside the gate of that name—the modern Yali Kiosk Kapoussi.[[8]] There the wall left the shore and made for the Strategion and the Thermæ of Achilles. The former was a level tract of ground devoted to military exercises—the Champ de Mars of Byzantium—and occupied a portion of the plain at the foot of the Second Hill, between Yali Kiosk Kapoussi and Sirkedji Iskelessi.[[9]] The Thermæ of Achilles stood near the Strategion; and there also was a gate of the city, known in later days as the Arch of Urbicius. The wall then ascended the slope of the hill to the Chalcoprateia, or Brass Market, which extended from the neighbourhood of the site now occupied by the Sublime Porte to the vicinity of Yeri Batan Serai, the ancient Cisterna Basilica.[[10]]
The ridge of the promontory was reached at the Milion, the milestone from which distances from Constantinople were measured. It stood to the south-west of St. Sophia, and marked the site of one of the gates of Byzantium. Thence the line of the fortifications proceeded to the twisted columns of the Tzycalarii, which, judging from the subsequent course of the wall, were on the plateau beside St. Irene. Then, the wall descended to the Sea of Marmora at Topi,[[11]] somewhere near the present Seraglio Lighthouse, and, turning northwards, ran along the shore to the apex of the promontory, past the sites occupied, subsequently, by the Thermae of Arcadius and the Mangana.