For safety reasons, tourists are strongly advised to avoid this region. Astonishingly shaped and immaculately white limestone concretions emerge from the "Great Sand Sea" discovered by the German Gerhard Rohlfs in 1873. Most impressive are the formations of Sahara el-Beida, where the rocks have been eroded in such a way as to resemble giant mushrooms, huge meringues or fantastical animals. Particularly magical at dusk.