Just for some background info, Berlin was the capital of the German Reich and after 1945 the allies and Soviets split Berlin into two. After that happened people tried to escape the Soviet occupied zone of Berlin and because of this the Soviets put up a wall and blocked people from leaving. This symbolized the divide of Berlin and increased tensions between the allies(at this point called NATO) and the Soviets. The Germans did not want to suffer another war and the tensions continued to go up. To answer your question this symbolized tensions growing between the Warsaw pact and NATO because the world was literally divided right at Berlin.