In 1879–1880, he led the first trans-Sahara expedition from Morocco to Senegal. The primary purpose of the expedition was to perform geological studies of the region, investigating the possibilities of iron ore deposits. In 1880, with his Spaniard companion Cristobal Benítez, he became only the fourth European to visit the fabled city of Timbuktu. The others being, Alexander Gordon Laing (1826), René Caillié (1828) and Heinrich Barth (1853).
Illustration of Tindouf Oasis (1880), from "Timbouctou : voyage au Maroc, au Sahara et au Soudan".
Selected publications
Ueber das Auftreten Jurassischer Gebilde in Böhmen, (On the occurrence of Jurassic build-up in Bohemia), (1870).
Skizzen aus Westafrika (Sketches of West Africa), (1878).
Lenz, Oskar (1884). Timbuktu: Reise durch Marokko, die Sahara und den Sudan, ausgeführt im Auftrage der Afrikanischen Gesellschaft in Deutschland in den Jahren 1879 und 1880 (2 Volumes) (in German). Leipzig: Brockhaus. Volume 1, Volume 2. Translated into French in 1886 by Pierre Lehautcourt.