What happened to russia's window by the sea

Poland was the only nation really created from alot of German land, other nations took off parts of Germany and the newly formed Lithuania took some land . Poland, which received the danzig corirdor to the Baltic sea(though not the city of Danzig itself) Russia's "window to europe/the world" was St. Petersburg which was built as a planned city specifically for that purpose and has always been Russian. 

Think of Germany having to accept all responsibilty for the worst war in history along with the economic problems the treaty caused in Germany and what they lead to, from there you can do your own homework though.