Towering skyward like an immortal sentinel, the Great Pyramid of Giza demonstrates the extraordinary engineering achievements of the Ancient Egyptians and embodies a level of engineering sophistication far superior to anything the world has produced in any subsequent epoch. At the time of its construction, during the Fourth Dynasty of Egypt's Old Kingdom, architecture was design; engineering was the means of evaluating, refining, and realizing those designs. As primitive as the engineering practices may have been in the 2500s B.C.E., the results were, and still are, completely astonishing. The Great Pyramid, for over four thousand years, was the tallest structure in the world. As the sole remnant of the Seven Wonders of the World, it attests to the breath-taking capabilities of the prevailing principles of architectural construction and engineering practices employed not only during that time period but even today. The sides of the Great Pyramid are aligned perfectly with the four cardinal points of the compass even though at the time, the compass had not even been invented; furthermore, the outside surface stones of the structure were cut within 0.01 inch of being perfectly smooth and were assembled at nearly perfect right angles, off by only .001 inch (Dunn 46). Modern technology still cannot place such 20-ton stones with greater accuracy. The length of each side of the pyramid at the base was 755 feet and the overall erection stood a staggering 481 feet (Chaney 12). It was constructed using 2,500,000 limestone blocks, each weighing on average 2.5 tons. An elaborate plan specifying the location of burial chambers, secret passages, and palaces was outlined, along with architectural constructing and engineering plans. Due to the limited technology, the ancient Egyptians relied on the cleverness of their primitive engineers, who ultimately devised every facet of the Great Pyramid. Like 20th century bridge designs, the pyramid contained cornerstones that had balls and sockets built into them, which subjected the structure to expansion and contraction movements from heat and cold, as well as from earthquakes, droughts, sandstorms, and other natural phenomena. Without these ingenious inclusions, the structure would have been significantly damaged throughout the years. The Great Pyramid was definitely not a product of 21st century engineering but was instead a construction whose engineering dates from the very edge of pre-history. Despite it's ancient status, it is one of the most astounding edifices ever created and is a statement about the great prowess of early Egyptian engineers.