the Seven Wonders of the Ancient World. Today it is the only one of those wonders still in existence. Zawyet el-Aryan This site, halfway between Giza and Abusir, is the location for two unfinished Old Kingdom pyramids. The northern structure's owner is believed to be pharaoh Nebka, while the southern structure, known as the Layer Pyramid, may be attributable to the Third Dynasty pharaoh Khaba, a close successor of Sekhemkhet. If this attribution is correct, Khaba's short reign could explain the seemingly unfinished state of this step pyramid. Today it stands around high; had it been completed, it is likely to have exceeded . Abusir There are a total of fourteen pyramids at this site, which served as the main royal necropolis during the Fifth Dynasty. The quality of construction of the Abusir pyramids is inferior to those of the Fourth Dynasty—perhaps signaling a decrease in royal power or a less vibrant economy. They are smaller than their predecessors and are built of low-quality local limestone. The three major pyramids are those of Niuserre, which is also the best-preserved, Neferirkare Kakai and Sahure. The site is also home to the incomplete Pyramid of Neferefre. Most of the major pyramids at Abusir were built using similar construction techniques, comprising a rubble core surrounded by steps of mudbricks with a limestone outer casing. The largest of these Fifth Dynasty pyramids, the Pyramid of Neferirkare Kakai, is believed to have been built originally as a step pyramid some high and then later transformed into a "true" pyramid by having its steps filled in with loose masonry. Saqqara Major pyramids located here include the Pyramid of Djoser—generally identified as the world's oldest substantial monumental structure to be built of dressed stone—the Pyramid of Userkaf, the Pyramid of Teti and the Pyramid of Merikare, dating to the First Intermediate Period of Egypt. Also at Saqqara is the Pyramid of Unas, which retains a pyramid causeway that is one of the best-preserved in Egypt. Together with the pyramid of Userkaf, this pyramid was the subject of one of the earliest known restoration attempts, conducted by Khaemweset, a son of Ramesses II. Saqqara is also the location of the incomplete step pyramid of Djoser's successor Sekhemkhet, known as the Buried Pyramid. Archaeologists believe that had this pyramid been completed, it would have been larger than Djoser's. South of the main pyramid field at Saqqara is a second