The most famous government building in Germany is the Reichstag in Berlin. Home to the national government, but also a beautiful building with public access to the roof.
To go into the building and up to the roof, it is best to plan in advance. Because of security you need an id and there’s only a limited amount of people going up at a time. To avoid standing in line for hours (especially in the summer), book a your tickets and a time online, so you’re sure to make the most out of your time in Berlin.
The view from the roof is spectacular. Walk around in the glass dome, all the way to the top and you’ll have a 360 degree view of Berlin.
The dome is also open at night, so if you also want to go up for a view in other places, you might consider doing the dome on the Reichstag at nighttime. Berlin by night.