In the Early Middle Ages significant interregional trading posts arose in the North Sea region. They were always located at the intersection of major roads and water routes. A castle was usually the seat of the local government. Hammaburg was a central town with crafts and trades as well. Melting pots are evidence of metalworking, antlers and bone remnants reveal bone carver's work and loom weights indicate the production of clothing. From the 9th century, products from many regions made their way to Hammaburg. Archaeologists have found wheel-thrown pottery from Rhineland, shell-tempered ware from the Frisian coastal area, Slavic pottery from the East and fine ceramics from the south of Francia. Grindstones made of Norwegian slate and basaltic scoria from the Eifel region give further evidence of interregional trading.