There is probably no railpass of use to you as you are not traveling all that much on trains - except for Nurnberg to Frankfurt the other trips are short - go to www.bahn.de - the German Railways web site for schedules and sample fares - for the longer journey you may want to book one of the limited in number discounted tickets online at bahn.de - but note that these are train-specific and cannot be changed nor refunded - but can be much much cheaper than full fare tickets.

You could check your other trips for discounts too if you can lock your times into stone and not want flexibility to change.

there are not problems usually traveling on trains in winter though if there is snow in that area - a relatively rare chance then trains could be late, etc but they will still get you there.

If you wanted complete flexibility to hop any train anytime then investigate the Germany Railpass which does exactly that - but you could save some money over the pass if you can get the discounted Nurnberg to Frankfurt ticket - anyway check the fares on bahn.de to see what that trip will cost - and for those discounted tickets booking early is imperative as they are sold in limited numbers and do sell out early sometimes.

For lots of great stuff on German trains check out these fab IMO sites - www.seat61.com (lots of good info on online discount tickets); www.budgeteuropetravel.com and www.ricksteves.com (the latter two have good info on passes, which are sold at German train stations so check at the Nurnberg Hbf (main station) about passes if they are good for you - and again they will only be viable if you want full flexibility to say hop any train Nurnberg to Frankfurt and on other trips as well - even then they may not be cost-effective so check and compare with normal fares on www.bahn.de.

Thks a lot for your suggestion, PalenQ. Accordting to our air ticket, we actually need to fly from NRB to FF and then catch international flight back to our country. This is the reason we plan to fly from NRB to FF and then just take train to Cologne. Is there a kind of rail pass, which is similar to Bayern ticket (euro 29 for 5 pax) and can use for the route above?

Well the Bayern Ticket is a Lander ticket - or ticket good in an area surrounding a big city or in a certain Land - or state - Germany is made up of many different Lands or states - so no to any railpass but perhaps Cologne and Frankfurt are in the same Land? Or Frankfurt and Heidelberg could be - or may not be - if they are use Lander Tickets of course - if not the fare Frankfurt to Cologne can be high so use the online discounts to save money. Frankfurt to Heidelberg should not cost that much.

But forget about German Railpass is flying Nurnberg to Frankfurt.

Noted with many thanks, PalenQ. We will try to find online discounts per your suggestion.

The best but not cheapest way is to use the ICE3 from Frankfurt airport to Cologne (about one hour) and from Cologne to Mannheim (about 1.5 hours) and then the regional train to Heidelberg. The normal ticket is consirably more expensive but maybe you can go for group rebates (groups normally start with 6 persons but it can be cheaper to buy for 6 than 5 single tickets).

From Heidelberg to Frankfurt airport exist some shuttle bus connections (by Lufthansa and other providers). They can be easier to use than a train, especially early in the morning.

Thks, Hans. Can we buy group ticket on DB machine?

There are two routes between Frankfurt and Cologne - the newer one is a high-speed ICE connections Hans talks about and IME you see very little countryside due to wind blocks on each side of an often recessed rail line - yet there is a more scenic way that would take about two hours I believe rather than one hour by the bullet train (going nearly 190 mph) - to take the classic old main rail route that goes along the Rhine River, thru the fabled Rhine Gorge and along the Rhine the whole way to Cologne - passing thru Bonn, a nice city where you could stop off for a few hours if you have time. And this route I believe may be cheaper than the high-speed route (but not sure of that).
Frequent trains on either route. I wonder if the group rebates for full fare tickets would be cheaper all told than the 29 euro fares often available online if you book far enough in advance?

PalenQ, you're right, the route on the left side of the Rhine is absolutely beautiful. If the time is available, taking it for at least one ride is worth it.

The 29 euro fares are probably cheaper than the group rebates but I think that they'e often sold out early while group rebates might still be available.

aple: I've never used them but just saw that they exist on the bahn website. I think there might only a limited number available for a train but I'm not sure.

The 29 euro fares are probably cheaper than the group rebates but I think that they'e often sold out early while group rebates might still be available.>

good point if not much more and readily available just wait and then decide which train to take rather than locking oneself or fiveselves into a non-changeable train-specifidc train days if not weeks in advance.

But OP should go to www.bahn.de and see what savings could be and what the group rates provide as well - a trip to the train information counter in Nurnberg Hbf - main station can supply all those answers as well - at least the full fare and group rate tickets.