Thirteen buttress-walls, pierced by three arches superposed, run transversely across the hall, from the wall AA to the wall BB, and divide the interior into fourteen compartments, which average nearly 10 feet in breadth, and vary in length from about 27 to 40 feet; the walls AA and BB standing further apart, as they proceed from south-west to north-east.

These compartments, excepting the first and last, were divided, as the cavities for fixing joists in the buttresses prove, into three stories of twelve chambers, the superposed arches affording continuous communication between the chambers on the different floors. The chambers on the ground floor, so far as appears, were totally dark, but those on the two upper stories received light and air through the large loophole in the wall BB, with which each of them was provided. The compartment C´ led to the chamber in the second story of the tower N, and at the same time communicated at v with the terrace on which the Palace of Blachernæ stood, and where the Mosque of Aivas Effendi is now erected.

The face of the wall AA is pierced by two tiers of loopholes, which are openings in two superposed corridors or galleries constructed in the body of the wall AA. These loopholes occur at irregular distances from the buttress-walls, and some of them are partially closed by the latter, while others are completely so.

As the galleries in AA are blocked with earth at various points, they cannot be explored thoroughly. At the north-eastern end, the upper gallery opens on the garden of a Turkish house near the Heraclian Wall. Whether the south-western end communicated with the court of the Palace of Blachernæ cannot be determined.

Returning to the vestibule b, and crawling next through the opening at i, the explorer finds himself in F, a vaulted chamber over 29 feet long, and about 17 feet wide. What the original height of the apartment was cannot be ascertained, the floor being covered with a deep bed of fine dark loam, but the ceiling is still some 23 feet high. Below a line nearly 14 feet from the ceiling, as a sloping ledge at that elevation makes evident, the north-eastern and north-western walls of the apartment are much thicker than above that point. Over the ledge in the north-eastern wall is a loophole.

The south-eastern wall is strengthened with two arches; while the ceiling is pierced by a circular hole, which communicates with the room on the higher story of the tower. When first explored by Dr. Paspates, a well nearly 18 feet deep was found sunk in the floor.[[522]]

Before leaving the chamber the explorer should notice the shaft of a pillar which protrudes from the south-western wall, like the shafts of the pillars built into the open sides of the tower N.

Returning once more to the vestibule b, we proceed to the breach in the wall g, and enter E. That the breach was made on a systematic plan is clear from the half-arch f, which was constructed to support the building after the wall g had been weakened by the opening made in it.

E was a stairway-turret, in which an inclined plane, without steps, winded about the newel, e, upwards and downwards. The turret is filled with earth to the present level of the vestibule b, so that one cannot descend the stairway below that point; but there can be no doubt whatever that the stairway conducted to the original floor of the vestibule b, and to the gateway l, and thence to the tunnel and postern in the counter-fort. Whether it led also to an entrance to the chambers C C C cannot be discovered under existing circumstances. The object of the breach in g was to establish communication between the stairway, the vestibule b, and the tunnel Z, after the original means of communication between them had been blocked by raising the floors of the tunnel and the vestibule to their present level, in the manner already described.

The stairway winds thirteen times about its newel, and ascends to within a short distance of the summit of the turret. The summit was open, and stood on the level of the court of the Palace of Blachernæ; but the opening could be reached from the stairway only by means of a ladder removable at the pleasure of the guardians of the palace, and was, doubtless, closed with an iron door for the sake of greater security.