West Berlin was once a little island in Eastern Germany and was surrounded by a 160km long wall. Nowadays you can walk or cycle along this former wall trail, visit the old border crossing stations, see old wall fragments and many different sights along the way. A part of that wall trail lies within the city of Berlin, but a large part also takes you to the outskirts of the city. It is very clearly sign-posted all along the course of the trail and you can easily follow the signs (walking or cycling), that are placed exactly at a height of 3.6 meters (the height of the former wall). We have taken parts of the inner city wall trail numerous times before and decided to walk a part of the outer city trail. We took the S-Bahn to "Griebnitzsee" station, got off the train, and walked down to the water to start this 12km long track by foot towards Wannsee. All around Berlin are many lakes and in this particular section, the wall used to run in the middle of the lake for a while. In the beginning, you are walking down streets, along the shores of the lakes, past beautiful old Villas, the castles Babelsberg and Glienicke, through the woods and along the water. About every other kilometre you will find a restaurant or beer garden to stop and take a break. And all in all, we walked about 4 hours in total, a walk packed with history, nature, a little rain (weather wasn't perfect..) and some exercise. I have included the link above to a page with lots of details on the wall trail, the course and the sights you find will find along the way which I hope is useful. I loved this as a Sunday activity and look forward to the next excursion very soon.