The landscape of Ancient Estonia featured numerous hillforts, some later hillforts on Saaremaa heavily fortified during the Viking Age and on to the 12th century. There were a number of late prehistoric or medieval harbour sites on the coast of Saaremaa, but none have been found that are large enough to be international trade centres. The Estonian islands also have a number of graves from the Viking Age, both individual and collective, with weapons and jewellery. Weapons found in Estonian Viking Age graves are common to types found throughout Northern Europe and Scandinavia.