The second sort of mosque is a domed, and sometimes vaulted building of a form chiefly suggested by the Byzantine domed churches, with a central space and four short arms. This sort of mosque became almost universal in Turkey and Egypt after the capture of Constantinople by the Turks, and the appropriation to Moslem worship of Santa Sophia itself. The tombs are ornate and monumental buildings, or sanctuaries, of the same general character as the domed mosques, and often attached to them. [Illustration: FIG. 186.--HORSE-SHOE ARCH.] From very early times the arches, in the arcades which have been described as virtually constituting the whole structure of the simpler sort of mosque, were pointed. Lubke claims as the earliest known and dated example of the pointed arch in a Saracenic building, the Nilometer, a small structure on an island near Cairo, which contains pointed arches that must have been built either at the date of its original construction in A.D. 719, or at latest, when it was restored A.D. 821. The Mosque of Amrou, however, which was founded very soon after the conquest of Egypt in A.D. 643, and is largely made up of materials obtained from older buildings, exhibits pointed arches, not only in the arcades, which probably have been rebuilt since they were originally formed, but in the outer walls, which are likely, in part at least, to be original. [Illustration: FIG. 187.--EXTERIOR OF SANTA SOPHIA, CONSTANTINOPLE. SHOWING THE MINARETS ADDED AFTER ITS CONVERSION INTO A MOSQUE.] Whatever uncertainty may rest upon these very remote specimens of pointed architecture, there is little if any about the Mosque of Ibn Tulun, also at Cairo, and built A.D. 885, or, according to another authority, A.D. 879. Here arcades of bold pointed arches spring from piers, and the effect of the whole structure is noble and full of character. From that time the pointed arch was constantly used in Saracenic buildings along with the semicircular and the horse-shoe arch (Fig. 186). From the ninth century, then, the pointed arch was in constant use. It prevailed in Palestine as well as in the adjacent countries for two centuries before it reached the West, and there can be no doubt that it was there seen by the Western Crusaders, and a knowledge of its use and an appreciation of its beauty and convenience were brought back to Western Europe by the returning ecclesiastics and others at the end of the First Crusade.[37]