In 1820–1825, on a scientific expedition to the Middle East with his friend Wilhelm Hemprich, he collected thousands of specimens of plants and animals. He investigated parts of Egypt, the Libyan Desert, the Nile valley and the northern coasts of the Red Sea, where he made a special study of the corals. Subsequently, parts of Syria, Arabia and Abyssinia were examined. Some results of these travels and of the important collections that had been made were reported on by Humboldt in 1826. While in Sudan he designed the mansion of the local governor of Dongola, Abidin Bey.