For this reason, and for protecting themselves from slave raids coming from Sudan, the shangul communities decided to establish their villages in naturally-defended hills and mountains, amidst rocky outcrops. Due to this harsh topography, houses and granaries were raised over stone pillars. German traveler Ernst Marno described shangul architecture and villages in his Reisen im Gebiete des Blauen und Weissen Nil (Vienna, 1874).