In the photo below you can see what looks like a party of tourists with a guide, all on Segways.
Even our hotel had a Segway for hire.
We didn't hire a Segway, but we did hire bikes from the Fat Tire shop near the Zoo train station [7 euros for 4 hours and the shop provides bike locks and helmets if you want them]. Berlin is very flat and has lots of dedicated bike lanes. Cycling is the best way to see the city. It was a lovely day and the best part of our ride was in the beautiful Tiergarten.