Next to the atrium was the narthex, or porch, which led to the church direct. Sometimes there was only the narthex without the atrium. A central avenue, or nave, with two aisles, and the semicircular apse at the end of the nave, was the usual interior form of the early basilicas. The nave was wide and lofty, and was usually divided from the aisles by two rows of columns, and from the apse by a large semicircular arch. The capitals of the columns carried the arcaded upper story, in the walls of which were the windows that lighted the church. In the oldest type of the basilica there was no window in the apse, so this portion of the church was bathed in a mysterious twilight, adding a poetic charm to the gold mosaics with which the roof of the apse was decorated. Sometimes windows were introduced into the low walls of the aisles; the aisles were covered with shed-like wooden roofs, which were supported on trussed framework. [Illustration: Fig. 331.—Ambo or Pulpit from St. George’s at Salonica.] Sometimes the trusses were ceiled, and on the ceilings were painted scriptural subjects. The wall spaces of the second story in the nave were also occupied with paintings of sacred subjects. The floor of the apse was raised higher than that of the nave, and was approached by steps; seats were placed around the wall of the apse for the priests, and in the centre was the elevated throne for the bishops. A portion of the nave space was sometimes appropriated for the choir, screened off by a marble structure, and at either end of the choir were placed the “ambos” or pulpits (Fig. 331). The altar was in the centre of the apse, generally over the tomb of a Christian martyr, and underneath all, or sometimes a portion only of the church, was the crypt.