Around 100km east of Robe, the fast-flowing Web River runs through a deep gorge and then cuts straight through a limestone hill. Though underground for only 1.5km, the aeons of erosion have carved 15km of passages. Proposed for World Heritage listing, the vaulted chambers, flying buttresses, massive pillars and fluted archway sometimes resemble an Antonio Gaudí cathedral. The cave is venerated by area Muslims due to Sheikh Sof Omar Ahmed reputedly taking refuge here in the 11th century. There’s a pilgrimage every November.
If you walk through you’ll cross the river seven times, either wading or swimming. It takes about two hours. You can also ride a four-passenger boat. Some Sof Omar villagers (none of whom speak English) act as guides and, though prices aren’t fixed, you can expect to pay Birr200 to walk through and Birr100 just to look around the entrance. They have torches, but for safe spelunking one is never enough; bring your own. From August to October the water is usually too high to get through, though the beautiful rock formations near its mouth can be seen any time. The guides at Bale Mountains National Park know about the cave’s water levels, and if you want someone who speaks English, you can hire one to come with you.
From the village of Goro, 60km east of Robe, buses leave for Sof Omar (Birr28, two hours) at 6am on market days (Thursday, Friday and Saturday), and return about 4pm. Other days you’ll have to rely on sporadic pick-up trucks. A few daily buses connect Goro to Robe (Birr35, two hours).