With a length of 15.1 kilometers, Sof Omar Caves is the longest cave in Ethiopia. It was Africa’s longest cave when it was measured in 1972. Since then, it has been surpassed by explorations in Madagascar (Ambatoharanana – Crocodile Cave 18.1 km) and Algeria (Rhar Bou Ma’za – the Tafna River Cave 18.4 km). The Weyib River (also known as the Gestro River) flows through it, and it is located east of Ginnir in the East Bale Zone of the Oromia Region in southeast Ethiopia. It disappears at the entrance to Ayiew Maco and resurfaces at the Holuca resurgence one kilometer (0.62 mi) distant. Tradition has it that a Muslim holy man by the name of Sof Omar and his daughter by the name of Ayiew both lived in the area.
Local terms for “name” and “cave,” respectively, are Maco and Holuca. It has been a longtime center for religion and is revered by Islam and the indigenous Oromo culture. The pillars in the caves, especially in the “Chamber of Columns,” are what makes them famous. The river eventually stopped flowing through the meander, leaving behind a dry valley that connected the resurgence at Holuca to the cave sink at Ayiew Maco. The town of Sof Omar is located in the arid valley not far from Ayiew Maco. After rising roughly 45 m above the Web due to valley infill, it descends to a pebble beach downstream of Holuca.
On the basalt plateau just above the cave, a massive shakehole measuring 100 meters (330 feet) in width and 60 meters (200 feet) in depth is the other prominent feature. A network of joints helps to build the cave; one set roughly goes north to south and the other travels east to west. The orientation of this network of passageways is southeast. There are 42 entrances to Sof Omar, however, typically only four can be used to enter:
• The Tourist Entrance downstream from the Holuca Resurgence at a location where the abandoned meander forming the dry valley rejoins the Web river; • Two upstream Settlement Entrances (one to the east and one to the west of the village);
• A right bank entrance that leads to the Deep South section of Clapham’s Climb Series, located downstream of Holuca.
When entering the cave through one of the Village Entrances, the visitor passes a villagers’ shrine. The Ayiew Maco Series is a collection of linked tunnels ranging from 1 to 10 meters wide. A number of people can cross through to the pebble beach on the river’s left bank. On the right bank, a less complicated network of passageways can be found. These were most likely connected to those on the left bank until the vadose action of the Web deepened the river passage and broke those connections.