Pumice is a volcanic rock that has special qualities. It combines a low density with strength and forms a very useful building material. The German Pumice Museum is in the Volcano geopark, where pumice has been mined since the mid-nineteenth century. The stone made it possible to produce lightweight concrete blocks that were particularly important for reconstruction after the Second World War. They require less structural support and smaller foundations than heavier materials and also have properties of thermal insulation. The open-air museum is set out like a block-making works of the post-war period. It shows mechanical excavators for mining the pumice, a travelling crane, a mill for making the concrete, and drying racks for the blocks, so visitors can see the whole process. There are also period machines and vehicles.