The Sof Omar Cave system is a spectacular natural and cultural landmark in Ethiopia, renowned primarily for being the longest cave in the country, with a surveyed length of 15.1 kilometers (9.4 miles). This vast underground labyrinth was carved out over millions of years by the Weyib (or Web) River, which vanishes into the limestone formation at one point and resurfaces about one kilometer downstream.

Geologically, it is famous for its breathtaking natural architecture, featuring colossal columns, high vaults, and fluted archways in chambers like the celebrated 'Chamber of Columns.' Culturally, the cave holds deep significance, as it is named after the Muslim holy man Sheikh Sof Omar, who is said to have sought refuge and worshipped there in the 11th century, making it an important Islamic pilgrimage site that predates the arrival of Islam in the Bale region. The cave system has an impressive total of 42 entrances and exits, underscoring its immense scale.