 Nature parks cover almost half the area of Franconia.In 1991 UNESCO recognised the Rhön as a biosphere reserve.Among the most picturesque geotopes in Bavaria, are the Franconian sites of "Fossa Carolina", the Twelve Apostle Rocks ("Zwölf-Apostel-Felsen"), the Ehrenbürg, the cave ruins of Riesenburg and the lake of Frickenhäuser See.