Architectural form in
Constantinople A cross-in-square church is centered around a quadratic
naos (the 'square') which is divided by four columns or piers into nine
bays (divisions of space). The inner five divisions form the shape of a
quincunx (the 'cross'). The central bay is usually larger than the other eight, and is crowned by a dome which rests on the columns. The four rectangular bays that directly adjoin this central bay are usually covered by
barrel vaults; these are the arms of the "cross" which is inscribed within the "square" of the naos. The four remaining bays in the corner are usually
groin-vaulted. The spatial hierarchy of the three types of bay, from the largest central bay to the smallest corner bays, is mirrored in the elevation of the building; the domed central bay is taller than the cross arms, which are in turn taller than the corner bays. To the west of the naos stands the
narthex, or entrance hall, usually formed by the addition of three bays to the westernmost bays of the naos. To the east stands the bema, or sanctuary, often separated from the naos by
templon or, in later churches, by an
iconostasis. The sanctuary is usually formed by three additional bays adjoining the easternmost bays of the naos, each of which terminates in an
apse crowned by a conch (half-dome). The central apse is larger than those to the north and south. The term
bema is sometimes reserved for the central area, while the northern section is known as the
prothesis and the southern as the
diakonikon. Evidence for Byzantine domestic architecture is scant; it appears that the core unit of the cross-in-square church (nine bays divided by four columns) was also employed for the construction of halls within residential structures.
Liturgical use The architectural articulation of the distinct spaces of a cross-in-square church corresponds to their distinct functions in the celebration of the
liturgy. The narthex serves as an entrance hall, but also for special liturgical functions, such as
baptism, and as an honored site of burial (often, as in the case of the
Martorana in
Palermo, for the founders of the church). The naos is the space where the congregation stands during the service. The sanctuary is reserved for the priests. The altar stands in the central bay, or bema, which is sometimes provided with a
synthronon, or bench, where the clergy may sit. The prothesis is used for the preparation of the
eucharist, and the diakonikon houses liturgical vestments and texts used in the celebration of the Liturgy.
Common variations in Constantinople The architectural form and liturgical function described above correspond to the "classic" type of the cross-in-square church, which is exhibited by a number of significant monuments (for example, by the
Myrelaion in
Constantinople). However, this classic type represents only one of a number of possible variations on the cross-in-square form. Particularly in later Byzantine architecture, the core of the cross-in-square plan could be augmented through the addition of peripheral structures. An example is provided by the
Chora Church in Constantinople. The original 11th-century cross-in-square was expanded in the 14th century through the addition of a second narthex to the west (
exonarthex, or outer narthex) and by a side chapel (
parekklesion) to the south, used for burials. The ultimate plans of many other Byzantine churches resulted from a similar diachronic succession of additions about a central, cross-in-square, core; for example,
Kalenderhane Camii in Constantinople, Çanlı Kilise in
Cappadocia, and the
Martorana in Palermo. One particularly common subsidiary structure, witnessed, for example, at Kalenderhane, the Chora Church, and the Martorana, was a bell-tower. in
Stilo. The
naos is the central liturgical area and
bema the sanctuary. On the other hand, a radically abbreviated, "compact" form of the cross-in-square existed, built without narthex and with the three apses adjoining directly onto the easternmost bays of the naos. This plan was particularly common in the provinces, for example in southern Italy, in
Sicily, and in Cappadocia. In this type of church, the templon barrier was often erected along the axis of the two eastern columns, thus enclosing the three easternmost bays within the sanctuary. A particularly important variation on the cross-in-square is the so-called "Athonite" or "monastic" plan, in which the rectangular bays at the north and south of the naos also opened onto semi-circular apses, giving the church the appearance of a
triconch. This plan, often held to be typical of monastic churches, seems to have developed on
Mount Athos in the eleventh century; the lateral apses provided a space for the performance of
antiphonal liturgical music by two monastic choirs. An important example of this type outside of Athos is the 14th-century church known as "Profitis Elias" in Thessaloniki. ==Decoration==