During WWII, the Ghent Altarpiece was kept by the Germans in the Altaussee mine, Austria, along with many other masterpieces seized all across Europe by the Nazi administration. At the beginning of WWII, the panels of the Altarpiece of the Mystic Lamb had been transferred to the French city of Pau. On August 3, 1942, the Germans robbed the panels and brought them over to the Bavarian Neuschwanstein Castle, from where they were transferred to the Salt Mine Altaussee in Austria, in 1944. You can see here the entrance to the "König Josef" chamber of the mine in which most of the loot of the Einsatzstab Rosenberg was stored. The Einsatzstab Rosenberg was the Party organization dedicated to appropriating cultural property during the Second World War.