Greek colonization began in the 8th-6th centuries BC as many Greeks settled in new areas where they established polis, or city-states. The Greeks chose to colonize the Black Sea area for economic and political reasons, finding the geography and climate suitable. Some of the earliest Greek colonies appeared on the northern and southern Black Sea coast, including cities like Odessos. These colonies became important trade centers and ports. The site of the ancient Greek colony of Odessos is now the modern city of Varna, Bulgaria, which occupies a wider area but preserves remnants of the original settlement like the Varna Archaeological Museum housing the famous Varna Gold Treasure.