It remained for the Imperial period to complete the development. Orders of columns were placed in zones one above the other; niches of richer type occupied the surface of the wall, and not infrequently they were placed one within the other; rounded and rectangular niches followed one another in a rhythmic sequence; columns and piers stood out in higher relief and the podium and architrave were broken above and below them. Gradually the orders and niches lost their original significance; they were looked upon merely as decorative motives, and as such followed a development of their own. They lent to the wall-surface an ever-increasing movement and rhythm as their forms grew richer and freer. This evolution can be seen upon the walls of Roman buildings which are yet standing; if in the cities of the eastern Mediterranean most of the monuments have fallen, the elements of their composition have been found and put together, as in the Nymphaeum at Miletus,[301] or the theatre at Ephesus,[302] and similar decoration can still be studied upon the walls of Ba’albek.[303] But in western Asia, and notably in Syria, the old classical love of unbroken wall-surfaces died hard--perhaps it may be said to have survived long into the Middle Ages in the smooth faces of dressed stone which give so much dignity to the Mohammadan buildings of Damascus and Aleppo. Older and simpler decorative forms continued to rule when in Rome the evolution had gone on to other stages. The façade of the Nabataean temple at Sî’, for example, echoes in free-standing architecture the features of the relief decoration of the Ephebeum at Priene.[304] In the temenos of the basilica at Apamea (second century A.D.) the solid outer wall has disappeared, and its place is taken by a series of piers with rectangular openings between, but in the basilica itself the treatment of the wall is still of an extremely simple character.[305] The temenos wall of the temple at Palmyra is treated with the old formal severity. At Bâqirḥâ and at Isriyyeh the walls are unbroken save by shallow pilasters,[306] a simplicity which rivals that of the pre-Roman tomb of Ḥamrath at Swaidâ.[307] At Mushennef and at Qanawât pilasters are set at the angles, and the rest of the wall is undecorated.[308] In the pre-Roman temple at Swaidâ, niches, in imitation of small doors, are placed on either side of the single entrance;[309] at ‘Atîl a double order of niches, the lower rectangular, the upper rounded and arched, occupy the same position, but the walls of the cella are without even the customary pilasters;[310] in the Qaisariyyeh at Shaqqâ a genuine opening flanks the doorway on either side, but the façade is otherwise unadorned.[311] In the Philippeion at Shahbâ the side niches are omitted and there are no pilasters except at the angles; rounded and rectangular niches are employed on the interior walls of the palace, and on either side of the interior doorways of the bath, but in all other respects the