the Baltic Sea       
noun uk/ˌbɔːl.tɪk ˈsiː/ us/ˌbɔːl.tɪk ˈsiː/ (also the Baltic)
 波罗的海
a sea in Europe between Denmark, Estonia, Finland, Latvia, Lithuania, Sweden, Germany, Poland, and Russia
  For a beach holiday, I recommend the island of Gotland, which lies in the middle of the Baltic Sea. 如果想去海滩度假,我推荐哥特兰岛,它位于波罗的海中部。 
 This victory established Russia as a major European power, and gained a maritime exit on the Baltic, where Peter founded his new capital, Saint Petersburg. 这场胜利确立了俄罗斯作为欧洲大国的地位,并为其获得了波罗的海的海上出口,彼得在那里建立了他的新首都圣彼得堡。 
 - More examples
 - The forests of the Baltic Sea area contain 90% of the world's amber, which is the best amber in the world.
 - A short hop from Finland, located on the Baltic’s breezy shoreline, Tallinn offers a slice of Scandinavia at a fraction of the cost.
 - Churchill famously pronounced that "From Stettin in the Baltic to Trieste in the Adriatic, an iron curtain has descended across the Continent."