Yes, three days is the right length for Berlin, and it is what we recommend for a first visit to a city this spread out. It splits cleanly into three: the historic Mitte core, the Brandenburg Gate, Reichstag dome, Holocaust Memorial, Museum Island, and Gendarmenmarkt on day one; the Wall and Cold War story, Checkpoint Charlie, Topography of Terror, and the East Side Gallery on day two; and a third day for the lived-in modern city, Prenzlauer Berg, the Mauerpark Sunday market, and the wide-open Tempelhofer Feld. You get the landmarks, the history, and one real neighborhood day rather than a pure sightseeing sprint. What still gets cut: Charlottenburg, the western side, and the lakes, which is exactly what a fourth day adds. This suits first-timers, couples, and anyone routing on to Prague next. Stay in Prenzlauer Berg: it is calm, pretty, and puts you on the doorstep of Mauerpark with easy tram and U-Bahn hops to Mitte. Register your free Reichstag dome slot and buy an ABC day ticket, controls are frequent.