Poland is located in Central Europe, bordered by Germany, Czech Republic, Slovakia, Ukraine, Belarus, Lithuania, and Russia. Its longest river is the Vistula. Key dates in Poland's history include becoming Christianized in 966, gaining independence in 1918 after being partitioned by neighboring countries starting in 1772, and the rise of the Solidarity trade union movement in 1980 that helped bring down communism in 1989. There are 23 national parks across Poland protecting landscapes like the Tatras Mountains and coastline on the Baltic Sea. The capital and largest city, Warsaw, is situated on the Vistula River in the center of the country.