[Illustration: S. SAVIOUR IN THE CHORA. ARCHIVOLT ON THE NORTH SIDE OF THE PARECCLESION.]
[Illustration: S. SAVIOUR IN THE CHORA. WINDOW HEADS IN THE CENTRAL APSE. _To face page 310._]
Two passages, which cut through the north wall, lead from the parecclesion to the church. Off the passage to the west is a small chamber whose use is not apparent. It may be simply a space left over when the chapel was added. Higher up, in the thickness of the wall, about ten feet from the floor, and a little above the springing level of the vaulting in the parecclesion, is a long, narrow passage, lighted by a window at the east end, and covered by a small barrel vault, corbelled at the springing, on two courses of stone and three courses of brick laid horizontally, thus narrowing the space to a considerable degree. From this corbelling spring the vaulting courses, which are steeply inclined and run from both ends to the centre, where the resultant diamond-shaped opening is filled in with horizontal courses (Fig. 48). On the north side of the passage is a broad opening roughly built up, but which seems originally to have communicated with the south cross arm. The opening is almost central to the cross-arm, and is directly above the doors leading from the church to the parecclesion.
The exterior of the parecclesion and the outer narthex are treated with arcades in two orders of the usual type. On the piers of the arcades are semicircular shafts which in the parecclesion rise to the cornice, but on the west front stop at the springing course. Here they may have supported the wooden roof of a cloister or porch. The apse of the parecclesion has five sides with angle shafts and niches, alternately flat and concave in three stories. The north wall is a fine example of simple masonry in stripes of brick and stone, and with small archings and zigzag patterns in the spandrils of the arches.
Below the parecclesion are two long narrow cisterns having their entrance on the outside of the apse.[540]
_The original plan of the church_ (Fig. 102). The greater part of the alterations made in the church date from Byzantine times, and the marble coverings then placed upon the walls have effectually covered up any traces which might have given a clue to the original form of the building. In consequence any attempt at restoration must be of a very tentative character.