The route of Bus 100 takes you from the Zoo to Alexanderplatz past many Berlin sights. Along the route is not only the Kaiser Wilhelm Memorial Church, various embassies, Bellevue Palace or the Kongresshalle, but also Reichstag and the Brandenburg Gate.

If you're parents are fit walkers, you can also walk parts of the route and hop on again at a later stop. This is especially recommended for the stretch from the Brandenburg Gate along Unter den Linden with its impressive Prussian buildings like Humboldt-Universität, Staatsoper and Kronprinzenpalais to the Berlin Cathedral.

And should your visits not be of the walking kind - not a problem at all. You can easily enjoy all the sights from the bus and the grandkids or son/daughter provide the commentary for the tour with stories from their personal lives - much better than the standard recorded audio commentaries on tours.