German Rail Pass Flexi

Of course it depends on your travel plans and behavior. If you plan to use trains in a travel day HoHo way (just catch the next one) the pass is a good and convenient choice; if you can plan more precisely single booking of trains can be a cheaper decision.

More info: https://int.bahn.de/en/offers/passes/german-rail-pass-flexi

Thanks so much …. Does this pass also work for the local trains such as ones within Frankfurt or trains within the city of Cologne etc.?

An answer to your question would require some work on our part. I have used a lot of GRPs myself. I can tell you that a GRP can be very handy. But whether it's worth the price depends on the price and convenience of the OTHER options available as well.

You would need to provide more complete information up front for a good comparison with the other ticketing options, starting with the ages of your family members and an itinerary with specific travel dates/times - assuming you know them ("etc." is not helpful information.) Also, what airport will you fly into? Out of? And are you only planning to visit these cities, or to venture outside these cities on day trips?

Hey Russ, just planning to be in those cities, flying in and out of FRA. 2 youth and 2 adults.

Without specific travel dates for each of your journeys, the price options for adult p2p saver fare (Sparpreis) tickets cannot be conjured up. For these same tickets there is no "youth" fare at DB, only free passage for "children" to age 14. The page MarkK provided explains this and additional details for save fares.

So for trips between the cities mentioned - looks like 5 trips on 5 different travel days if your last trip is Heidelberg > Frankfurt Airport - you'll need to enter your own best guesses for dates, times, ages, etc. on your own at the DB itinerary search page, then do the math to compare your results with railpass prices and then do your own analysis. Expect to spend some learning-curve time:

https://int.bahn.de/en/

A good analysis will consider the additional advantages of the railpass... the total flexibility of travel day/time, the lack of consequences for missing a train or for boarding the wrong train, the ease of purchasing one pass instead of multiple tickets, etc.

You have also asked about "trains within cities." The S-Bahn trains can be used with a railpass. However, with a flexi-pass, S-Bahn train rides on days that you are NOT moving between cities would require the purchase of ADDITIONAL travel days beyond the 5 travel days you have mentioned. Examples...

1) On Friday you use 1 day of a 5-day railpass to take your first long train trip, the one from Frankfurt to Berlin, for a 4-night stay. You arrive at some station in Berlin, then drop bags at hotel. THEN you decide to take the S-Bahn to Potsdam for the afternoon. No problem. Hop on any S-Bahn train(s) you like that same day.

2) Same Friday trip to Berlin... then on Saturday you want to go to Potsdam. Using up one of your 5 travel days for this trip would leave you one travel day shy for the rest of your trip :( :(

So if you intend to use the S-Bahn with a rail pass throughout your stays in Cologne, Berlin, Frankfurt, you will need either a CONTINUOUS pass or a flexi-pass with additional travel days. Yes, it will add significantly to the price of your pass as you start adding days for inner-city travel like this.

Here is a map of Berlin's S-Bahn train system for your reference:
https://upload.wikimedia.org/wikipedia/commons/e/e2/Topographischer_Netzplan_der_S-Bahn_Berlin.png

In reality, the "trains within cities" idea doesn't work out all that well because so many places you might like to go, especially in a city like Berlin, are not near enough to an S-Bahn stop. On top of the S-Bahn, you will probably need to use the U-Bahn (subway) or city buses to get where you want to go, and these are NOT covered by any of the German Rail passes. What you will probably need are local tickets that cover you for ALL the local transportation - S-Bahn, U-Bahn, buses, trams - which you would purchase separately from either your rail pass or your p2p saver fares:

Berlin: https://www.vbb.de/en/tickets/

Thanks so much this is great information and so detailed. I really appreciate u putting in so much effort into this. Looking forward to our visit. Certainly planning on doing the most recommended FrankfurtonFoot tour with MsJo.

Also one last question- if we visit Heidelberg on Dec 24th, will there be anything in the town. I know the castles closes at 2 pm so after we r done with the castle will there be anything to do in the town on Christmas Eve?

Heidelberg on the afternoon of the 24th will be a ghost town. As will just about everywhere else. Some restaurants may be open, but they usually only serve reserved tables, and even then, there will be more of those on the 25th. Even the 26th will be very limited as that's also a holiday. Good time to take pictures though.

I think the Winter Garden in Karlsruhe is open on the 26th. That's a 45 minute train ride from Heidelberg.