The Great Pyramid of Giza is the largest Egyptian pyramid and the tomb of Fourth Dynasty pharaoh Khufu. It was built in the early 26th century BCE during a period of around 27 years. Initially standing at 146.6 m, 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 m. The base was measured to be about 230.3 m square. The Great Pyramid was built by quarrying an estimated 2.3 million large blocks weighing 6 million tonnes in total.