The Great Pyramids of Giza It's 756 feet long on each side, 450 high and is composed of 2,300,000 blocks of stone, each averaging 2 1/2 tons in weight. Despite the makers' limited surveying tools no side is more than 8 inches different in length than another, and the whole structure is perfectly oriented to the points of the compass. Until the 19th century it was the tallest building in the world and, at the age of 4,500 years, it is the only one of the famous "Seven Wonders of the Ancient World" that still stands. It is the Great Pyramid of Khufu, at Giza, Egypt. Some of the earliest history of the Pyramid comes from a Greek traveller named Herodotus of Halicanassus. He visited Egypt around 450 BC and included a description of the Great Pyramid in a history book he wrote. Herodotus was told by his Egyptian guides that it took twenty-years for a force of 100,000 oppressed slaves to build the pyramid. Stones were lifted into position by the use of immense machines. In 1638 a English mathematician, John Greaves, visited the pyramid. He discovered a narrow shaft, hidden in the wall, that connected theGrand Gallery with the descending passage. Both ends were tightly sealed and the bottom was blocked with debris. Some archaeologists suggested this route was used by the last of the Pharaoh's men to exit the tomb, after the granite plugs had been put in place, and by the thieves to get inside. Given the small size of the passageway and the amount of debris it seems unlikely that the massive amount of treasure, including the huge missing sarcophagus lid, could have been removed this way. Some have suggested that the pyramid was never meant as a tomb, but as an astronomical observatory. Richard Proctor, an astronomer, did observe that the descending passage could have been used to observe the transits of certain stars. He also suggested that the grand gallery, when open at the top, during construction, could have been used for mapping the sky. Most archaeologists, though, accept the theory that the great pyramid was just the largest of a tradition of tombs used for the Pharaohs of Egypt. So what happened to Khufu's mummy and treasure? Nobody knows. Extensive explorations have found no other chambers or passageways. Still one must wonder if, perhaps in this one case, the King and his architects out smarted both the ancient thieves and modern archaeologists and that somewhere in, or below, the last wonder of the ancient world, rests Khufu and his sacred gold.