above each arm of the cross and one above the central bay where the arms intersected. The western arm of the cross extended farther than the others, forming an atrium. The design details are a matter of some dispute. The contemporary historian Procopius (c. 500–565) gives the following description: Two straight lines were drawn, intersecting each other in the middle of the form of a cross, one extending east and west, and the other which crossed this running north and south. On the outside these lines were defined by walls on all of the sides, while on the inside they were traced by rows of columns standing above one another. At the crossing of the two straight lines, that is to say at about the middle, there was set aside a place which may not be entered by those who may not celebrate the mysteries; this with good reason they call the "sanctuary." The two arms of this enclosure which lie along the transverse line are equal to each other, but the arm which extends toward the west, along the upright line, is enough longer than the other to make the form of the cross. That portion of the roof which is above the sanctuary, as it is called, is built, in the center at least, on a plan resembling the Church of Sophia, except that it is inferior to it in size. The arches, four in number, rise aloft and are bound together in the same manner and the circular drum which stands upon them is pierced by windows, and the dome which arches above this seems to float in the air and not to rest upon solid masonry, though actually it is well supported. Thus, then, was the central part of the roof constructed. And the arms of the building, which are four,... were roofed on the same plan as the central portion, but this one feature is lacking: underneath the domes the masonry is not pierced by windows. A tenth-century poem by Constantine the Rodian, or Constantine of Rhodes, preserved in a fifteenth-century manuscript, contains an ekphrasis and description of the church. The domes appear to have been drastically altered between 944 and 985 by the addition of windowed drums beneath all five domes and by raising the central dome above than the others. The 12th-century writer Nicholas Mesarites also recorded a description of the church ,