On the way southeast out of Berlin, you should take a ride along Mühlenstraße and visit the East Side Gallery. Famous for many reasons, the East Side Gallery is one of the largest open-air art exhibitions in the world, as well as the one that has existed for the longest time. It features murals by artists from all over the world, painted in 1990, just after East suddenly became West, and the overpowering desire for freedom dissolved what was known as the "Anti-Fascist Protection Rampart" (In German: Antifaschistischer Schutzwall).
For more than four decades, the underground fortress, with it's heavy artillery guns, monitored all Warsaw Pact naval vessels, entering and leaving the Baltic Sea. The fortress was constructed to withstand a nuclear attack, and packed with radar, sonar and hydrophones, it could monitor all movements in the western Baltic, and react instantly in the event of an attack.