Sof Omar Cave is the longest cave in Ethiopia at 15.1 kilometres (9.4 mi) long; sources claim it is the longest system of caves in Africa. It is situated to the east of Robe, in the Bale Zone of the Oromia Region in southeastern Ethiopia (6°55′N40°45′E), through which the Weyib River (Gestro River) flows. It sinks at the Ayiew Maco entrance and reappears at the Holuca resurgence 1 kilometre (0.62 mi) away. According to tradition Sof Omar was the name of a Muslim holy man who lived in the area and Ayiew the name of his daughter. Maco and Holuca are local names for 'name' and 'cave', respectively. Long a religious centre, it is sacred both to Islam and the local Oromo traditional religion.