The first pyramid, as we would recognize the structure today, appeared in the Fourth Dynasty in the reign of Snofru who completed two pyramids at Dashur as well as finishing the work begun on his father’s pyramid at Meidum. These pyramids also made use of the gradation of stone blocks of limestone but the blocks were cut smaller as the structure rose, providing a smooth outer surface instead of the 'steps' which was then covered in limestone. The most outstanding example of pyramid building in Egypt was the Great Pyramid of Khufu at Giza, the last remaining of the Seven Wonders of the Ancient World, with a base covering thirteen acres and composed of 2,300,000 stone blocks. Known as the Horizon of Khufu in ancient times, the pyramid was positioned for precise astrological alignment.