Hochland von Adamaua
At the behest of the German African Society, which commissioned him to explore the entire Benue River basin, Flegel undertook further study of the Benue, and in 1880 travelled up the Niger to Sokoto. There, he obtained leave from the sultan for an expedition to the Adamawa Plateau. During his exploration of the Benue, he identified its source at Ngaundere in 1882.