A number of West Slavic Polish tribes formed small states, beginning in the 8th century, some of which later coalesced into larger states. Among these tribes were the Vistulans ("Wiślanie") in southern Poland, with Kraków and Wiślica as their main centers (major fortified centers were built in their country in the 9th century), but later the tribe(s) referred to as the Polans ("Polanie"—literally, "people of the fields") would prove of decisive historic importance. At the end of the 9th century Vistulans were part of the Great Moravia, according to some theories.