Sof Omar Natural Cave
An Extraordinary longest natural cave system in Africa is called Sof Omar. It extends at 15.1 kilometres (9.4 mi) long; sources claim it is the longest system of caves in Africaand ranks as the 306th longest in the World. , it has over 42 entrances, although only a han dful is actually used to gain access nowadays.
It is situated to the east of Robe, in the Bale Zone of the Oromia Region in southeastern Ethiopia (6°55′N 40°45′E / 6.917°N 40.75°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. Long a religious centre, once the refuge of a medieval Muslim holy man, the Sof Omar Cave remains a sacred site , currently it is sacred both to Islam and the local Oromo traditional religion. The caves are known for their many pillars, particularly in the "Chamber of Columns".