Days in Berlin Following Tour

Certainly I would suggest a visit to Potsdam, maybe even for 2 days and not just one. Would you consider a visit to Sachsenhausen Concentration Camp or to Ravensbrück? Does the RS tour include a visit to the Olympic Stadium, Wannsee Villa or Track 17? Check out some of the themed tours that are on offer in Berlin, such as a Cold War Tour, 3rd Reich, Jewish Berlin, Underground Berlin, etc.
I like Insider tours, but there are other good tour companies operating there too, just not the "free" ones and if you want to book ahead, do it directly with the companies and not with Viator or Trip Advisor.

Berlin is one of my favorite cities. I there in October and followed Ms.Jo’s advice on the Insider’s Tours. Mine was led by a graduate student in architecture who gave me new insights into the history and architecture of Berlin. I also took the Secret Food Tour of Berlin. It was a great introduction to the multi-cultural food of Berlin. I will be back in February for another work event and plan on spending more time exploring Museum Island and taking advantage of some of the other suggestions the Ms. Jo has made.

There is so much to do that an additional 3 days will probably still not seem enough time.

Sandy

Think it is a good idea to have some more time in Berlin.

You will likely be there at second weekend of Festival of Lights (date open) which is a really scenic event. The parallel "Berlin leuchet" is also a light artists event at the same dates.

For local culture visit our week(end) markets on Saturdays and the flea markets on Sundays, e.g. "my" one at Boxhagener Platz - or the ones at Kollwitzplatz or Winterfeldtplatz (rainbow area).

In the evening you can enjoy shows, theatres etc., e.g. English Theatre Berlin. If date of travel comes closer have a look into VisitBerlin event calendar.

Also Potsdam has a lot to explore beyond the palaces - Potsdam itineraries for 1, 2 and 3 day(s).

I'd also look at the Original Berlin Walks walking tours. They seemed to have specialized tours about different aspects of Berlin that might be more in depth than RS.

Berlin is a big city with lots of things to see and 4.5 days is in my opinion not enough to do it justice.

I've never taken the tour but recently made my first visit to Berlin. I had 4-1/2 days (5 nights) there and I would have like a few more days. I did a day trip to Potsdam which took up the better part of one day so basically I had 3-1/2 days in Berlin itself and there is so much to see and do.

My sister and I spent 10 days in Berlin last year and found plenty of things to keep us busy. We did take a day trip to Potsdam on the public transportation, did a couple of walking tours, would have taken what sounded like a really terrific food tour but ran out of time... "Always leaving something to come back for", right? We spent our arrival day out in the fresh air at the Zoo. Lots of great advice already posted. It is really an amazing city; I can't wait to return.

The Wannsee Villa ( House of The Wannsee Conference ) is an underappreciated place , particularly if you have an interest in the history of the second war . https://en.wikipedia.org/wiki/Wannsee_Conference

We now regularly plan a food tour in larger cities -- mainly because the first we ever did was fantastic . . . and it was in Berlin. Highly encourage you to check it out: https://www.berlinfoodtour.de/tours/berlin-mitte-food-tour/

Wow! Even though it's many months away, our excitement for visiting Berlin is building based on all the responses. Thanks to all of you for your responses and suggestions!!! We'll definitely extend our stay in Berlin beyond what we originally planned.

Happy Travels to everyone!
David

I see that the RS tour day in Berlin includes the Bundestag. It would be worthwhile to check in advance (as in soon) to make sure you actually get to visit the inside of the building (highly recommended!). If not, you can schedule this on your own; you do need to make an advance appointment online. I was in Berlin for six days, and look forward to visiting again--I feel that time barely touched the surface of all there is to experience in this city.