Poland Kruszwica tower erected on the Lake Gopło. The first historically documented ruler of Poland, Duke Mieszko I, had his palace on an island in the Warta River in Poznań. Nowadays the Polish lakes provide a location for the pursuit of water sports such as yachting and wind-surfing. The Polish Baltic coast is approximately long and extends from Świnoujście on the islands of Usedom and Wolin in the west to Krynica Morska on the Vistula Spit in the east. For the most part, Poland has a smooth coastline, which has been shaped by the continual movement of sand by currents and
Mieszko I of Poland poses some problems of interpretation of the information regarding the attack of Margrave Gero on the Slavic tribes, as a result of which he purportedly "subordinated to the authority of the Emperor Lusatia and the Selpuli" (meaning the Słupian tribes) "and also Mieszko with his subjects". According to the majority of modern historians, Thietmar made an error summarizing the chronicle of Widukind, placing the Gero raid there instead of the fighting that Mieszko conducted at that time against Wichmann the Younger. Other sources make no mention of such conquest and of putting the Polans state on the same footing with