The wall is flanked by three fine hexagonal towers, built towards their summit in brick, perhaps, as Dr. Paspates[561] suggests, in order to lighten the weight of constructions erected on marshy ground. They are among the finest towers in the circuit of the fortifications. The interior of the southernmost tower, the only one which can be safely examined, measures 32-½ by about 19 feet, and was in three stories. Upon the face of the tower is an inscription, in letters formed with pieces of marble, in honour of the Emperor Michael, probably Michael II. Between the first and second towers is a gate, named the Gate of Blachernæ (πόρτα τοῦ Μονοτείχους τῶν Βλαχερνῶν),[562] after the quarter before which it stood. [Illustration: General View of the Walls of the City From The Hill On Which The Crusaders Encamped in 1203.] It has been generally supposed that the Wall of Heraclius comprised not only the portion of the city walls just indicated, but the whole line of fortifications extending from the Kerko Porta to the Golden Horn.[563] The evidence on the subject is, however, in favour of the opinion that the Wall of Heraclius was only the portion of the fortifications before us. It is the extent implied in the description of the Heraclian Wall, as a wall erected to bring the Church of Blachernæ within the line of the city bulwarks.[564] That is an apt description of a wall extending from the foot of the Sixth Hill to the Golden Horn; it is a very inadequate description of a line of bulwarks from the Kerko Porta to the harbour. In the next place, more extensive fortifications were not required to protect the church, seeing it was well defended on the south by the acropolis on the western spur of the Sixth Hill. All that was necessary for the further security of the church was a wall on the west side of the plain on which it stood. Furthermore, the fortifications extending from the Kerko Porta to the foot of the Sixth Hill, commonly ascribed to Heraclius, have been proved to be the work of other hands, the greater part being the Wall of Manuel Comnenus,[565] while the remainder formed, originally, the defences of the Fourteenth Region. The Wall of Leo the Armenian was erected in 813 to strengthen the defence of this part of the capital, in view of the preparations which the Bulgarians under Crum were making for a second attack upon Constantinople.[566] Crum had retired from his first assault upon the city, resolved not only to retrieve the defeat he had sustained, but also to punish the treacherous attempt upon his life, when he was proceeding to negotiate terms of peace with the emperor.