The northern quarter of Kairwán is almost wholly taken up by the Great Mosque, which is only approached by narrow lanes. The exterior has been well described by Mr. Rae, and can hardly be said to be particularly imposing. The south-east end of the Mosque measures 85 yards. A single porch in its centre is appropriated exclusively for the entrance of the Bash-Mufti. The sides of the building are 143 yards in length, and each possesses four entrance porches, the finest of these facing the ramparts. Mr. Rae thus describes it: “It has an outer horse-shoe arch, and an inner one which contains the door opening direct into the prayer- chamber. The exterior is a finely proportioned piece of Saracenic work: it has a row of arched panels along the upper portion of its sides, and the dome and interior of its arches are in plaster fretwork.” Midway, on the same side, is the sacred well of _Kefâyat_ (Plenty). It is fenced in by a low wall, its aperture is lined with different coloured marbles, and tradition asserts that it communicates directly with the spring of Zemzem at Mecca. It has hardly ever failed to yield a plentiful supply of water. The north-west end is somewhat narrower than that facing the south-east. It measures only 75 yards across, and the Minár rises in its centre. The four porches on both sides of the building correspond, and they are divided by enormous buttresses of solid masonry. The interior of the Mosque may be divided into the prayer-chamber (40 yards in length by 85 in breadth), the vestibule adjoining it, and a great cloistered court. The roof of the prayer-chamber is loftier than that of the vestibule, and that of the vestibule higher than that of the court. The prayer-chamber is divided into a great central nave, with eight aisles on each side of it. These are formed by parallel rows of ten columns each, the two nearest to the eastern wall being close together. The pillars of the lesser aisles are of various-coloured marble, and are about fifteen feet in height. The capitals in many cases evidently do not belong to the columns on which they rest, but they are generally of white marble or stone. From the capitals spring semicircular arches supporting a flat ceiling of dark-coloured wood. In the south-west walls of the prayer-chamber, thirteen columns are embedded in the masonry, three close together on one side of the porch, and one on the other. The latter evidently came from some Byzantine church, and its capital consists of a grotesque arrangement of birds and flowers. The columns of the central nave are at least twenty-two feet high. Their arches support a wall covered with tracery, and a lofty circular roof. The nave terminates in a dome lighted by small painted-glass windows. Two groups of four columns each mainly support the weight of the cupola. The _mihráb_ niche in the east stands between two red porphyry pillars of great beauty, and is lined with delicate mosaic in marble and lapis- lazuli.