If you only get one stop alone in Berlin, make it Reichstag Dome (free, book ahead, audio guide). Next on our list are Tempelhofer Feld (free, 300 ha former airfield) and East Side Gallery (free, 1.3 km of Wall murals); the other three, down to Teufelsberg, are below with where to book.
ex-listening station, street art
free, 1.4 km open-air exhibit
free, open 24 h, 2,711 stelae
free, 1.3 km of Wall murals
free, 300 ha former airfield
free, book ahead, audio guide