Olorgesailie is a geological formation in East Africa, on the floor of the Eastern Rift Valley in southern Kenya, 67 kilometres (42 mi) southwest of Nairobi along the road to Lake Magadi. It contains a group of Lower Paleolithic archaeological sites. Olorgesailie is noted for the large number of Acheulean hand axes discovered there that are associated with animal butchering. According to the National Museums of Kenya, the finds are internationally significant for archaeology, palaeontology, and geology.