Great Pyramid at Giza. The only surviving wonder of the ancient world is the Great Pyramid. It was built nearly 5,000 years ago, as the tomb of the Egyptian pharaoh Khufu (or Cheops, as the Greeks called him), who ruled about 2700 B.C. Covering an area of 13 acres at this base, the pyramid contains nearly 2,500,000 well-cut stone blocks. Each block weighs about 21/2 tons, although some weigh many tons more. At its peak the pyramid originally rose to a height of 481 fee. The area it occupies could contain four of the largest European churches, including the Basilica of St. Peter in Rome. Yet the men who built it did not have even draft animals, let alone machinery. Even the wheel was unknown to them, and the huge stone blocks were hauled on wooden sledges by gangs of laborers. The only mechanical aids they had were rollers, levers, and bronze cutting tools. Yet in spite of these difficulties, the Great Pyramid is so accurately constructed that a razor blade can hardly be inserted between the close-fitting casing-stones. The building is so precisely aligned that the errors of a modern magnetic compass can be checked against it.