Berlin was a key strategic city during the cold war because

After world war 2 Germany was split up in parts Russia had berlin. They built the Berlin Wall and separated the east and West Berlin the West Berlin held all of the housing and weapons used for the war. Hope this helps

Berlin was the heart of the Iron Curtain that Churchill predicted. The Berlin Wall had the advantage of being able to host both Soviet and Allied weaponry. Also, the division of the city along with Germany represented different ways of dealing with the fall of Nazi Germany. America used Germany economically while the Soviets left East Germany to, frankly, rot and die.