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. If we are to believe the Anonymus and Codinus, this was the circuit of Byzantium from the foundation of the city by Byzas to the time of Constantine the Great. On the latter point, however, these writers were certainly mistaken; for the circuit of Byzantium was much larger than the one just indicated, not only in the reign of that emperor, but as far back as the year 196 of our era, and even before that date.[12] The statements of the Anonymus and Codinus can therefore be correct only if they refer to the size of the city at a very early period. One is, indeed, strongly tempted to reject the whole account of this wall as legendary, or as a conjecture based upon the idea that the Arch of Urbicius and the Arch of the Milion represented gates in an old line of bulwarks. But, on the other hand, it is more than probable that Byzantium was not as large, originally, as it became during its most flourishing days, and accordingly the two arches above mentioned may have marked the course of the first walls built beyond the bounds of the Acropolis. We pass next to the third line of walls which guarded the city, the walls which made Byzantium one of the great fortresses of the ancient world. These fortifications described a circuit of thirty-five stadia,[13] which would bring within the compass of the city most of the territory occupied by the first two hills of the promontory. Along the Golden Horn, the line of the walls extended from the head of the promontory to the western side of the bay that fronts the valley between the Second and Third Hills, the valley of the Grand Bazaar. Three ports, more or less artificial,[14] were found in that bay for the accommodation of the shipping that frequented the busy mart of commerce, one of them being, unquestionably, at the Neorion.[15]