Hinterbruhl - a town in the district of Modling in the Austrian state of Lower Austria. It is home to the Seegrotte, a system of caves including Europe's largest underground lake. During the Second World War, a satellite camp of Mauthausen concentration camp was opened inside the caverns, producing parts for the HE 162 jet fighter. This card features the Husaren Temple built by Prince Johann of Liechtenstein in remembrance of the battles of Aspern and Deutsch-Wagram. Legend has it that 4 Husaren soldiers saved the life of the prince; however, this is just a legend and there are no written records to prove it. Seven Austrian soldiers, who were killed in the battles against Napoleon were buried in the temple.