Cambridge Ancient Hi.. - Index of

eligious architecture 961
Beroea and Zorava. Before the recent discovery of a second aisled tetraconch
at Bostra, these churches had all been identified as cathedrals under
the patriarchate of Antioch, where the cathedral initiated by Constantine
(327–41) was likewise built on a centralized plan – that of an octagon with
wooden dome – of which only a general written description survives. Of
these churches, only that at Apamea had central supports strong enough to
take a masonry dome. The L-shaped piers in the others probably offered
sufficient support only for thin upper walls under a light roof in wood. 70
Two other churches of the sixth century may be compared with the aisled
tetraconch churches of the eastern provinces: Sts Sergius and Bacchus, built
at Constantinople by Justinian in 524–7, and S. Vitale at Ravenna, built
between c. 526 and 547. Sts Sergius and Bacchus is a variant of the Bostra
group of aisled tetraconches in that its inner chamber and ambulatory are
inscribed in a square building with internal diagonal corner niches (Fig. 58).
The inner chamber is composed of eight wedge-shaped piers between which
four diagonal columnar exedrae alternate with three straight colonnades and
the arched opening into the eastern apse. The eight piers support a masonry
melon dome divided by ribs into sixteen segments. The dome does not rest
on pendentives, but rises from the walls built above the eight supporting
arches. The upper arcades of the nave, which open into the galleries, rest on
a richly carved flat entablature which incorporates a verse inscription in raised
lettering. Originally the church opened on the north side into the palace of
Hormisdas and on the south into the basilical church of Sts Peter and Paul
(built in 519) with which it shared a narthex, atrium and propylaeum. 71
Entered across an atrium and through a double-apsed oval narthex,
S. Vitale at Ravenna differs from the centralized churches discussed so far
in being octagonal both in its inner chamber and outer walls. As in Sts
Sergius and Bacchus, the inner octagon is composed of eight wedgeshaped
piers, but here seven columnar exedrae and the sanctuary open
between them. S. Vitale is eastern in style, rather than Italian, in its inclusion
of gallery over the cross-vaults of the ambulatory, in its marble decoration,
and in its walls, built of thin bricks with thick mortar joints rather
than the local short, thick bricks. The dome, however, is distinctly
Ravennate, made of earthenware tubes laid in horizontal courses, rather
than of brick. Unlike the low-slung dome of Sts Sergius and Bacchus, the
dome of S. Vitale rests on a drum pierced by eight windows over a zone of
squinches between its eight lower arches. 72
What may have been the largest church built at Constantinople before
Justinian’s St Sophia was the church of St Polyeuctus erected by Anicia
70 Kleinbauer (1973).
71 Mango, Byzantine Architecture 101–7; Mango, Studies on Constaninople xiii,xiv.
72 Krautheimer, Early Christian and Byzantine Architecture 169–70; Mango, Byzantine Architecture 132–4,
138, 140.
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