The crest for the city of Hamburg prominently features a castle which represents the Hammaburg that was built by order of Charlemagne around the year 808 AD. Subsequently the castle was attacked and destroyed, by Vikings, then rebuilt no less than 8 times. Hamburg really got a boost when, in 1189, Frederick I granted it the status of a Free Imperial City and tax free access into the North Sea. This made the city a major port in Northern Europe. In more recent times, they have discovered that in fact, Frederick I died before he could sign this actual document but they were successful in convincing others that he had done so.