Going on a Viking cruise with stop to Berlin, train ride to Berlin and back, looking for a local guide to show us the highlights in the time we have there. Any Rick Steves local guides to do this?
Besides possible recommendations for guides I recommend taking a Hoho bus tour because Berlin is huge and the top 10 of Berlin are widely spreaded - not in walking distance for an afternoon only. Here is another top 10 list which includes the recommended Berlin Wall Memorial.
Is this some sort of river cruise or is it an ocean cruise docking at a Baltic Sea port? If the latter: This topic has come up before, and the usual recommendation is not to try for Berlin because such a large amount of your time will involve sitting on a bus. There are good options much closer to the Baltic ports.
I loved the six days I spent in Berlin back in 2015 and look forward to returning. However, a lot of what is special about Berlin is the historical sights and the great museums. Those are not places to be appreciated as you drive by. Berlin itself doesn't have a lot of beautiful, old architecture as you can find in some other German cities.