I visited Berlin in Fall 2017, and while it was a pretty busy visit, had a wonderful time and wanted to share some fun aspects of the city with those who are considering going there.
Something important to keep in mind about Berlin for those flying from the US is the challenge of getting there: I flew one of the very last direct flights aboard Air Berlin (RIP). Berlin has multiple airports but most flights that go there have connections in other cities like Amsterdam.
Once you do arrive, there is more than an abundance of things to do. Below you can see some Trabant Tours available. The Trabant "is an automobile which was produced from 1957 to 1990 by former East German car manufacturer VEB Sachsenring Automobilwerke Zwickau. It is often seen as symbolic of the former East Germany and the collapse of the Eastern Bloc in general."
You can drive at your own speed and see the sights of Berlin from behind the wheel of a colorful vintage Trabant! I did see some of these tours encountering automotive difficulties, but they looked like a lot of fun.