Pyramid of Giza

Contrary to the common belief, only the Great Pyramid of Khufu (Cheops), not all three Great Pyramids, is on top of the list of Wonders. The monument was built by the Egyptian pharaoh Khufu of the Fourth Dynasty around the year 2560 BC and tooks over 20 years to be completed.

The site was first prepared, and blocks of stone were transported and placed. An outer casing (which disappeared over the years) was then used to smooth the surface. Although it is not known how the blocks were put in place several theories have been proposed.

One theory involves the construction of a straight or spiral ramp that was raised as the construction proceeded. This ramp, coated with mud and water, eased the displacement of the blocks which were pushed (or pulled) into place. A second theory suggests that the blocks were placed using long levers with a short angled foot.

When it was built, the Great pyramid was 145.75 m (481 ft) high. Over the years, it lost 10 m (30 ft) off its top. It ranked as the tallest structure on Earth for more than 43 centuries, only to be surpassed in height in the nineteenth century AD. It was covered with a casing of stones to smooth its surface (some of the casing can still be seen near the top of Khefre's pyramid).

The sloping angle of its sides is 51 degrees and 51 minutes. Each side is carefully oriented with one of the cardinal points of the compass, that is, north, south, east, and west. The horizontal cross section of the pyramid is square at any level, with each side measuring 229 m (751 ft) in length. The maximum error between side lengths is astonishingly less than 0.1%.

The structure consists of approximately 2 million blocks of stone, each weighing more than two tons. It has been suggested that there are enough blocks in the three pyramids to build a 3 m (10 ft) high, 0.3 m (1 ft) thick wall around France.