The Great Pyramid of Giza is the largest Egyptian pyramid and the tomb of Fourth Dynasty pharaoh Khufu. Built in the early 26th century BC during a period of around 27 years, the pyramid is the oldest of the Seven Wonders of the Ancient World, and the only one to remain largely intact. As part of the Giza pyramid complex, it borders present-day Giza in Greater Cairo, Egypt.

At completion, the Great Pyramid was cased entirely in white limestone. Precisely worked blocks were placed in horizontal layers and carefully fitted together with mortar, their outward faces cut at a slope and smoothed to a high degree.

Initially standing at 146.6 meters, the Great Pyramid was the tallest man-made structure in the world for more than 3,800 years. Over time, most of the smooth white limestone casing was removed, which lowered the pyramid’s height to the present 138.5 meters. What is seen today is the underlying core structure. The base was measured to be about 230.3 meters square, giving a volume of roughly 2.6 million cubic metres, which includes an internal hillock.

The Great Pyramid was built by quarrying an estimated 2.3 million large blocks weighing 6 million tonnes in total. The majority of stones are not uniform in size or shape and are only roughly dressed. The outside layers were bound together by mortar. Primarily local limestone from the Giza Plateau was used. Other blocks were imported by boat down the Nile: White limestone from Tura for the casing, and granite blocks from Aswan, weighing up to 80 tonnes, for the King’s Chamber structure.

There are three known chambers inside the Great Pyramid. The lowest was cut into the bedrock, upon which the pyramid was built, but remained unfinished. The so-called Queen’s Chamber and King’s Chamber, that contains a granite sarcophagus, are higher up, within the pyramid structure. Khufu’s vizier, Hemiunu (also called Hemon), is believed by some to be the architect of the Great Pyramid. Many varying scientific and alternative hypotheses attempt to explain the exact construction techniques.

There are two entrances into the pyramid: the original and a forced passage, which meet at a junction. From there, one passage descends into the Subterranean Chamber, while the other ascends to the Grand Gallery. The original entrance is located on the north side, 15 royal cubits (7.9 m; 25.8 ft) east of the centerline of the pyramid. Before the removal of the casing in the middle ages, the pyramid was entered through a hole in the 19th layer of masonry, approximately 17 meters above the pyramid’s base level.

For more than 4,000 years, Khufu reigned as the tallest building in the world. In fact, it took modern man until the 19th century to build a taller structure. Amazingly, the nearly symmetrical Egyptian pyramids were built without the aid of modern tools or surveying equipment.

According to Wikipedia