The Pyramids of Egypt are among the largest structures ever built and constitute one of the most potent and enduring symbols of Ancient Egyptian civilization. Most were built during the Old and Middle Kingdom periods. The shape of Egyptian pyramids is thought to represent the primordial mound from which the Egyptians believed the earth was created. The shape is also thought to be representative of the descending rays of the sun, and most pyramids were faced with polished, highly reflective white limestone, in order to give them a brilliant appearance when viewed from a distance. Pyramids were often also named in ways that referred to solar luminescence. For example, the formal name of the Bent Pyramid at Dahshur was The Southern Shining Pyramid, and that of Senwosret at el-Lahun was Senwosret is Shining.The first historically documented Egyptian pyramid is attributed to the architect Imhotep, who planned what Egyptologists believe to be a tomb for the pharaoh Djozer. Imhotep may have been the first to conceive the notion of stacking mastabas on top of each other, creating an edifice comprised of a number of "steps" that decreased in size towards its apex. The result was the Step Pyramid of Djozer, which was designed to serve as a gigantic stairway by which the soul of the deceased pharaoh could ascend to the heavens. Such was the importance of Imhotep's achievement that he was deified by later Egyptians.The most prolific pyramid-building phase coincided with the greatest degree of absolutist pharaonic rule. It was during this time that the most famous pyramids, those near Giza, were built. Over time, as authority became less centralized, the ability and willingness to harness the resources required for construction on a massive scale decreased, and later pyramids were smaller, less well-built and often hastily constructed.