For these sanctuaries were situated precisely at the foot of the western spur of the Sixth Hill, the site of the former being marked by the Holy Well of Blachernæ at Aivan Serai, that of the latter by the Holy Well in the ground between the Wall of Heraclius and the Wall of Leo. It is also in favour of the presence of fortifications on the spur in the seventh century to find that the historians of the Avar siege are silent as to any danger incurred by the Palace of Blachernæ, which stood on the spur, when the Church of St. Nicholas was burnt down, and when the Church of Blachernæ narrowly escaped the same fate. A similar silence is observed as to any advantage derived by the palace from the erection of the Wall of Heraclius, at the close of the war. But the age of these fortifications may be carried back to a still earlier date than the seventh century; for, according to the _Notitia_, the Fourteenth Region of the city, which stood on the Sixth Hill, was defended by a wall of its own, _proprio muro vallata_, so as to appear a distinct town.[460] The fortifications on the Sixth Hill may therefore claim to have originally constituted the defences of that Region, and therefore to be as old, at least, as the reign of Theodosius II. But although the origin of the fortifications around the western spur of the Sixth Hill may thus be carried so far back, it is a mistake to regard them as a structural prolongation of the Theodosian Walls. On the contrary, they are distinct and independent constructions. They proceed northwards, while the latter make for the north-east; so that the Wall of Anthemius, if produced, would stand to the east of the former, while the Wall of the Prefect Constantine under similar circumstances would cut them transversely. Furthermore, the outer wall, north of the Kerko Porta, is built almost at right angles against the wall of the Prefect Constantine, with a distinct line of junction, and stands so close to the Kerko Porta that the gate, what with the wall on one side and the tower screening the western façade of the Palace of Porphyrogenitus[461] upon the other, is almost crushed between them. Such a situation could never have been assigned to the gate, if the walls on either hand belonged to the same construction. It should also be added that the masonry of the walls around the spur is different from that in the Walls of Theodosius.