Murasia

The Lost Kingdom of Murasia was a civilization that once dominated the Earth of the Sonic X universe. Its people were incredibly advanced, having developed technology rivaling or surpassing that of present day civilizations and developed super-powerful alloy Emurasium. However, the Murasians were destroyed when their continent was rocked by a massive volcanic eruption, leaving behind only a small island with a handful of ruins to mark the passing of their great civilization. Dr. Eggman later invaded this island in an attempt to conquer the world by triggering an eruption like that which had destroyed the Murasians, but was thwarted by Sonic the Hedgehog and his allies. The island subsequently sank into the ocean, leaving behind only a few Murasian artifacts.