The eastern part of Berlin is not prosperous and is under strict Communist rules
The western part of Berlin is Prosperous and is under the USA's aid
The western part of Berlin attract a lot of visitors from the Eastern part as it has a lot of cinemas , shops , etc. The USSr sees it as a Capitalist infection in the heart of the eastern part of Germany
The western part of Berlin provides an easy escape route from East to West Germany fro some 250,000 refugees each year