Simplify the following text for a Grade 6 native English-speaking person.
Original: The eastern parts of the Gulf of Finland belong to Russia , and some of Russia 's most important oil harbors are located farthest in , near Saint Petersburg ( including Primorsk ) . As the seaway to Saint Petersburg , the Gulf of Finland has been and continues to be of considerable strategic importance to Russia .
Simplified: At the bottom of the gulf of Finland is Russia and its most important coast city St. Petersburg .