Ben Amera is Africa's largest monolith rising 633m above the desert floor. It's the world's second largest monolith only behind Uluru, in Australia. Locals will tell you that geologists think it might be larger than Uluru if the rock that lies beneath the Saharan sands were included in the measure of its size. Ben Amera is located in Mauritania, near the border with Western Sahara. It lies 4km north of the train track where the famous Iron Ore Train travels between Nouâdibhou and Choûm.