The unwritten record of history is preserved in buildings—in temples, fortresses, sanctuaries, and cities constructed of brick and stone. Early efforts to build permanent shelter were limited to the materials at hand. The trees of a primeval forest, the clay and mud of a river valley, the rocks, caves, and cliffs of a mountain range afforded only primitive opportunity for protec- tion, security, and defense and few examples survive. But the stone and brick of skeletal architectural remains date as far back as the temples of Ur built in 3000 ., the early walls of Jericho of 8000 ., and the vaulted tombs at Mycenae of the fourteenth.
