This is not the Schmöckwitz line out of Berlin. The GPX works east from Gleisdreieck through Kreuzberg and Neukölln, then on via Adlershof and Köpenick. After that, the city starts to thin out: Müggelheim, forest near the Müggelsee, then Erkner. From Grünheide, the route follows the quieter eastern corridor towards Hangelsberg and Fürstenwalde, with pine woods, Spree-side country and long flat stretches. No big climbs, but a proper change from inner Berlin to Brandenburg.