My travels then took me to the Great Pyramid of Giza, also known as the Pyramid of Khufu or the Pyramid of Cheops. It is the oldest and largest of the pyramids in the Giza pyramid complex bordering present-day Giza in Greater Cairo, Egypt. It is the oldest of the Seven Wonders of the Ancient World, and the only one to remain largely intact. The pyramid was built as a tomb for the Fourth Dynasty Egyptian pharaoh Khufu and estimate that it was built in the 26th century BC during a period of around 27 years. Initially standing at 146.5 meters (481 feet), 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 454.4 ft. What is seen today is the underlying core structure. The base was measured to be about 755.6 ft square, giving a volume of roughly 92 million cubic feet, which includes an internal hillock. The Great Pyramid was built by quarrying an estimated 2.3 million large blocks weighing 6 million tons 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 tons, 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 Queen's Chamber and King's Chamber, that contains a granite, 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.