The Art And Architecture of Islamic Cairo

10 The Art and Architecture of Islamic Cairo
Opening on to the river on the west side was the River Gate flanked
by two large circular towers, the ruins of which survive today. 8 It is
estimated that the fortress could maintain a garrison of 1,000 men
and this number could be doubled in times of emergency. 9
Of the surviving circular towers, only the remains of the southern
structure are externally visible. The northern tower is now incorporated
into the monastery of St George. The south tower is a hollow
cylinder, 34 metres in diameter, made of smooth cut stone at the
base and alternating courses of rougher stone and flat brick above.
The tower contained an inner cylinder forming two concentric circles
in the plan. The space between these cylinders was sectioned by radiating
walls, like the spokes of a wheel, dividing the outer circle into
eight rooms. As W. B. Kubiak has noted, this unique structure was
most likely designed to withstand water pressure rather than siege
engines. 10 It probably guarded the bridge of boats linking Babylon to
Rawdah Island, as well as the entrance to Trajan’s Canal. The southern
gate, or Iron Gate, served as the main entrance and access to this
was also by water. The remains of this gate can now be seen under
the Church of the Virgin, or al-Muallaqa church, which is built over
two of its south-western bastions. Whether a town existed outside
the fortress walls at the time of the Arab siege has been a matter of
debate. Ancient sources give conflicting evidence, but more recently
Kubiak has pointed to archaeological evidence suggesting traces of
earlier perimeter walls enclosing a larger settlement. The fact that by
639 Babylon had contracted to accommodate a smaller population
indicates there was no significant population outside the walls
except scattered monasteries and farmsteads. 11
More significantly, the population that eventually took up
residence outside the fortress was Amr’s army which, since the capture
of Bilbays, had constantly been on the move awaiting reinforcements.
When a force of 12,000 men eventually arrived,
including some of the best commanders the Arabs could muster, he
was in a position to take on the Byzantine forces deployed around
the tip of the Delta. Now based in Heliopolis, Amr managed to
draw the Byzantines into open battle, and in July 640 he crushed
their army by dividing his forces and attacking them from the
front, flank and rear. The remnants of the Byzantine army took
refuge in Babylon and Amr set up his encampment on its northern
side. They were unable to take the fortress because of their inexperience
of siege warfare, and what was left of the Byzantine army
could not challenge Amr’s military superiority. The situation was a
stalemate and throughout the lengthy investment a number of