Great Pyramid Of Giza / Pyramid Of Khufu, Egypt

The Pyramid of Khufu is the oldest and largest of the three pyramids in Giza, on the outskirts of Cairo in Egypt. It is believed the pyramid was built as a tomb for 4th dynasty Egyptian pharaoh Khufu, and was constructed over a 20-year period. The pyramid remained the tallest man-made structure in the world for nearly 4,000 years, unsurpassed until the Spire of Lincoln Cathedral was completed in the 14th century. The Great Pyramid consists of an estimated 2.3 million limestone blocks. There have been varying scientific and alternative theories about the Great Pyramid's construction techniques. It is estimated that completing the building in 20 years would involve moving an average of more than one block into its place every five minutes, day and night. At completion, the Great Pyramid was covered by white casing stones that formed a smooth outer surface. What is seen today is the underlying core structure. Some of the casing stones that once covered the pyramid can still be seen around the base. The casing stones were fit together with extremely high precision. The mean opening of the joints was only half millimeter wide. The accuracy of the pyramid's workmanship is such, that the four sides of the base have an average error of only 58 millimeters in length. The base is horizontal, and flat, to within 15 millimeters. There are three known chambers inside the Great Pyramid. The so-called Queen's and King's Chambers are higher up within the structure. The lowest chamber, which was never finished, is cut into the bedrock upon which the pyramid was built. Today, tourists enter the Great Pyramid via the Robber's Tunnel, dug by workmen employed by Caliph al-Mamun around year 820. The Queen's Chamber is accessed via a steep, and very narrow, ascending passage. At the upper end, the passage joins the Grand Gallery, which is 8.6 meters high and over 46 meters long, and slopes upwards leading to the King's Chamber. The only object in the King's Chamber is a rectangular granite sarcophagus, which is roughly finished, and has a broken corner.