The marble casing of the church is remarkably fine. Worthy of special notice is the careful manner in which the colours and veinings of the marble slabs are made to correspond and match. The zigzag inlaid pattern around the arches also deserves particular attention. High up in the western wall, and reached by the wooden stairs leading to a Turkish wooden gallery on that side of the church, are two marble slabs with a door carved in bas-relief upon them. They may be symbols of Christ as the door of His fold (Plate IV.). [Illustration: PLATE XLVIII. (1) S. MARY DIACONISSA. EAST END, NORTH SIDE (LOWER PART). (2) S. MARY DIACONISSA. EAST END, NORTH SIDE (UPPER PART). _To face page 186._] The church has a double narthex. As the ground outside the building has been raised enormously (it rises 15-20 feet above the floor at the east end) the actual entrance to the outer narthex is through a cutting in its vault or through a window, and the floor is reached by a steep flight of stone steps. The narthex is a long narrow vestibule, covered with barrel vaults, and has a Turkish wooden ceiling at the southern end. The esonarthex is covered with a barrel vault between two cross vaults. The entrance into the church stands between two Corinthian columns, but they belong to different periods, and do not correspond to any structure in the building. In fact, both narthexes have been much altered in their day, presenting many irregularities and containing useless pilasters. Professor Goodyear refers to this church in support of the theory that in Byzantine buildings there is an intentional widening of the structure from the ground upwards. 'It will also be observed,' he says, 'that the cornice is horizontal, whereas the marble casing above and below the cornice is cut and fitted in oblique lines.... The outward bend on the right side of the choir is 11-1/2 inches in 33 feet. The masonry surfaces step back above the middle string-course. That these bends are not due to thrust is abundantly apparent from the fact that they are continuous and uniform in inclination up to the solid rear wall of the choir.'