Gdańsk is a Polish city on the Baltic coast, at the centre of the country's fourth-largest metropolitan area. The city lies on the southern edge of Gdańsk Bay (of the Baltic Sea), in a conurbation with the city of Gdynia, spa town of Sopot, and suburban communities, which together form a metropolitan area called the Tricity (Trójmiasto). Gdańsk is Poland's principal seaport as well as the capital of the Pomeranian Voivodeship. The city is close to the former late medieval/modern boundary between West Slavic and Germanic lands and it has a complex political history with periods of Polish rule, periods of German rule, and extensive self-rule, with two spells as a free city. It has been part of modern Poland since 1945.Together with the nearby port of Gdynia, Gdańsk is also an important industrial centre. Historically an important seaport and shipbuilding centre, Gdańsk was a member of the Hanseatic League. The city was the birthplace of the Solidarity movement which, under the leadership of political activist Lech Wałęsa, played a major role in bringing an end to Communist rule across Central Europe.