Geography of Poland today's modern Polish society. The ancestors of today's Poles, the Polanie, built their first fortresses on islands in these lakes. The legendary Prince Popiel ruled from 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
Spytihněv I, Duke of Bohemia Spytihněv I, Duke of Bohemia Spytihněv I (c. 875 – 915), a member of the Přemyslid dynasty, was Duke of Bohemia from 894 or 895 until his death. He was the eldest son of Duke Bořivoj I, the first historically documented Bohemian ruler, and his wife Ludmila. Spytihněv and his younger brother Vratislaus were still minors at the time of their father's death about 889, and the Bohemian lands were placed under the regency of their suzerain, the Great Moravian ruler Svatopluk I. After Svatopluk died in 894, an inheritance conflict arose between his sons Mojmír II and Svatopluk II.