near Cairo, as well as the site of Buto, but is also attested in many other places in the Delta to the Faiyum region. This culture was marked by development in architecture and technology. It also followed its predecessor cultures when it comes to undecorated ceramics. Copper was known, and some copper adzes have been found. The pottery is hand-made; it is simple and undecorated. Presence of black-topped red pots indicate contact with the Naqada sites in the south. Many imported vessels from Palestine have also been found. Black basalt stone vessels were also used. People lived in small huts, partly dug into the ground. The dead were buried in cemeteries, but with few burial goods. The Maadi culture was replaced by the Naqada III culture; whether this happened by conquest or infiltration is still an open question. The developments in Lower Egypt in the times previous to the unification of the country have been the subject of considerable disputes over the years. The recent excavations at Tell el-Farkha (:de:Tell el-Farcha), Sais, and Tell el-Iswid have clarified this picture to some extent. As a result, the Chalcolithic Lower Egyptian culture is now emerging as an important subject of study. Gallery Upper Egypt Nabta Playa Nabta Playa was once a large internally drained basin in the Nubian Desert, located approximately 800 kilometers south of modern-day Cairo or about 100 kilometers west of Abu Simbel in southern Egypt, 22.51° north, 30.73° east. Today the region is characterized by numerous archaeological sites. The Nabta Playa archaeological site, one of the earliest of the Egyptian Neolithic Period, is dated to circa 7500 BC. Also, excavations from Nabta Playa, located about 100 km west of Abu Simbel for example, suggest that the Neolithic inhabitants of the region were migrants from Sub-Saharan Africa. Tasian culture The Tasian culture was the next in Upper Egypt. This culture group is named for the burials found at Der Tasa, on the east bank of the Nile between Asyut and Akhmim. The Tasian culture group is notable for producing the earliest blacktop-ware, a type of red and brown pottery that is colored black on the top portion and interior. This pottery is vital to the dating of Predynastic Egypt. Because all dates for the Predynastic period are tenuous at best, WMF Petrie developed a system called sequence dating by which the relative date, if not the absolute date, of any