Can I hop off Train for quick visit of city/town en route to final destination?

If you are using point to point tickets for specific train/date then generally no - you would have to purchase separate tickets for each leg of the journey. If you are traveling with a pass (unless you have a specific reservation for the full journey with the pass) or a regional ticket that covers travel for a specific period of time then you can.

I'm not sure about Belgium, but I can say about Germany. Optional reservations are only for a specific train (date and time), but full fare tickets are fully flexible within a certain time period after you start your trip. For trips under 100 km, you must finish by midnight the day you start; for longer trips by midnight the second day. Regional passes (Länder tickets) and national passes (Schönes-Wochendende, QdLT) are hop on/off for the entire day. Advance purchase, discounted Savings Fare tickets are for specific trains, but, as George said, you can build in stopovers of specific times using the Stopover function on the DB website.
 
Actually, only the Bahn trains (ICE/IC/EC/IR) are "specific" on a Saving Fare ticket. You are allowed to use any regional train on the same route to get to and from the express trains as long as you specify a regional train for that segment and use it between midnight (morning) that day and 10 AM the following day.
 
I'm not sure about this route (Köln to Brussels). Trains on this route tend to be Thalys, and they have reserved seats only, so you can't just hop off and on them. You might be able to take an ICE and hop off in Liege and hop on the next one, but they only run every four hours. Ask at a ticket desk if you can do this. If you book an ICE or a Thalys to Liege, and a regional train from there to Brussels, I would think you could use any regional train that day.

I don't know if you just picked Liege out of a hat as an example or if you are actually considering going there. If the latter, and if you don't have a special need to go there like family ties, you might scroll back to the recent discussion about the appeal (or lack thereof) of Liege.

Thank you to all for this insight. Will check out the DB site and the regional/fast train options. And regarding Liege as Nigel has referenced, no family ties, just afraid i will regret not seeing the landsape and smelling the air in the Wallonia region by heading directly to Brussels or Bruges. Thanks again!

Liège again... trust us, unless post-industrial decay, seedy gambling parlors and red light districts appeal to you (or it's late and night and you want to party a little), there's no good reason to stop in Liège. The station looks kind of interesting, but that's about it. If you really want a little taste of Wallonia, get it in Tournai, Namur, Spa, Dinant, or Durbuy.

Now, to anwser your question a little more directly... if you're taking the high speed Thalys train from Köln to Brussels, no, you can't get off and hop on a later train. Your ticket is valid for a specific seat on a specific train only. If your trip that day ends in Brugge, yes, you can take a little while to walk around Brussels, because Thalys only goes as far as Brussels and you can ride any later Belgian rail train to Brugge.

Taking the slower, non-Thalys method from Köln to Brussels and stopping in Liège...maybe. But as noted again and again... why?

Lee also mentioned the ICE that originates in Frankfurt and stops in Köln and Liège on the way to Brussels. As he notes, this train only runs a few times a day and it's operated by Deutsche Bahn, not Belgian rail. But, if you take this train, there's no reason you couldn't choose Liège as your terminal destination on the ticket, then just buy another ticket on Belgian rail after you've walked around the Liège a little and discovered for yourself why we're telling you it's not worth your time. Unlike the ICE train operated by Deutsche Bahn, Belgian rail (named SNCB in Wallonia, NMBS in Flanders) does not offer advanced purchase discounts or seat reservations, so there's no cost advantage of buying in advanced. Just buy the ticket at the station after asking yourself "Why did I think it was a good idea to stop and waste my valuable vacation time in place like Liège?", and procede to your next, far more worthwhile destination.

Unless of course you want to post something to the "Places I've Regretted Going" thread - then by all means - stop! ;)

If all these people telling you Liege is not worth a stop really know what they are talking about, then they must have stopped there. So at one point they must have felt it was worth a stop. Hmm.

I did not comment on the value of stopping in Liege because I haven't been to Liege.

However, if you think you might like Liege, don't let the naysayers dissuade you. It's possible that they like other things than you like, or that they just didn't do their research and know where to look. Do your own research. Liege has a website at www.liege.be. They say that Liege is "... the most important tourist city in Wallonia". The website has a link to a brochure you can download. Decide for yourself.

Some people like or dislike the same thing. While some people sing the praises of Baden-Baden, I thought it was totally ugly. I didn't go to the casino (gambling is not my thing). I've been to some small town Black Forest spas that were far more pleasant to me than the descriptions of those in Baden-Baden. They have a 2 block pedestrian street lined with glitzy shops, kind of a Rodeo Drive of Germany, that left me cold. I would discourage anyone from going to Baden-Baden, but then everyone should decide for themselves. I was also unimpressed with Reutte. I felt downtown was kind of shabby, much less attractive than Pfronten, just a few km away in Germany.

BTW, you might went to research Aachen.

Your time is limited, so it's OK to be choosy and to skip cities that you've heard of, but which may turn out to be known for their size, not their interest. (If you have a lot more train travel, then a Germany or Germany-Benelux railpass can be very convenient to use in those countries, jumping on most daytime trains (except Thalys) without any reservation required.)

@Laura -

I don't know how long you have been following the Helpline but if it has been for some time (or if you can make the search function work) you will see many threads where people ask about the balance of a railpass in Belgium and/or Germany. If you look at the detail and the examples which have been worked out by Russ, Lee, Tim, Tom, et al, you will see that it is very rare that a pass is economical in Belgium and with all the specials in Germany including Laender tickets and QDL tickets German passes are frequently uneconomical.

I will agree with you that the key is a LOT of long distance high speed travel. And I will agree with you about the convenience. It is always worth it to mention the tradeoff of cost to convenience.

It's also worth mentioning that Belgian rail neither requires nor offers reservations on any of their domestic trains and has no advanced purchase discounts, so the only thing a 3rd party rail pass does there is charge you far more than you need to pay. And maybe skipping, at the absolute most, a 10 minute wait to buy a ticket from the counter.

My wife and I recently spent an evening in Liège with two native Liègeois friends I had met at a language immersion course. I have to admit that now I see why locals, particularly the younger generations, love their town so much. It offers quite a bit of nightlife, and accompanied by people who knew the city, I had a great time. But even they admit that Liège is kind of run down and not very attractive. So I stand by my prior statements. Unless you have several weeks to kill in the low countries, you have a particular academic interest rust belt cities, or you have friends or family to visit in the area, Liège simply doesn't offer the kind of stuff most tourists travel to Europe to experience. Your valuable travel time is best spent elsewhere. If you really want to experience an interesting or attractive Wallonian city, choose Tournai instead.

"They have a 2 block pedestrian street lined with glitzy shops, kind of a Rodeo Drive of Germany, that left me cold."

Interesting comment. My neighbor described that section of Baden-Baden as "Rodeo Drive for Russian oligarchs with too much money and not enough good taste."

I have a similar question to the one above, and hope I can get your advice. My daughter is flying into Amsterdam, but will spend time in Belgium (about an hour out of Brussels). We're trying to figure out the best options for transportation which also have flexibility. We've looked at the 3 country pass, but I can't tell if it's very flexible on get on/get off. If you have to book a certain train time/seat, how far ahead do you have to do that? Also if she uses the pass to get to and from the Amsterdam Airport to Brussels will that count for two of her days. (Not sure if that is the most economical way to get to Brussels from Amsterdam.) She'll be in the Netherlands/Belgium area for 7 days. She may also want to go to Germany.

Any advice on the best way to travel in this area would be helpful. Also, do you know if the regional trains (if there are any) will take Visa?

Thanks.

Some on this site have said that Dutch Rail only accepts "chip and pin" cards. I don't have first hand knowledge, just heard. However, German Rail ticket machines do accept "strip" cards. The tutorial for ticket machines (in German, click "Erste Schritt" > "Bezahlen") on the German Rail website even shows how to insert strip cards (with the strip down and to the right). I've used strip cards in Bahn ticket machines, but not for a few years.

Additionally, if the machines won't accept a magnetic stripe card (without the chip and pin), she should be just fine going to the customer service desk and purchasing through them.

"she should be just fine going to the customer service desk and purchasing through them"

Not, as I understand, in the Netherlands, but yes, she should be able to in Germany (but then, all Bahn machines should take strip cards, so no need).

Lee, are you saying that the ticket machines are the only way to buy rail tickets in Netherlands? You can't buy tickets at a counter from a person anywhere?

Re: "academic interest in rust belt cities" Liege, Charleroi? In northern France that's called Germinal country.

All DB machines take US magnetic stripe credit cards, no need at all for a pin and chip card. Using that US credit card on a DB machine always went through for me. Of course, you can do the same at a staffed counter in Germany if you prefer that over dealing with the Automat, ie, paying with that magnetic stripe card.

@ Nancy,

Of course they have ticket counters in the Netherlands, but I've heard that they also only accept cards that are C&P.

I've never been in the Netherlands. I only know what I've read here. Can someone who's been there confirm this?

But I'm sure they take cash.

As of last Fall, you can buy a ticket at the counter with a standard US card. As I remember there is a small surcharge for using the ticket counter. The ticket machines only take chip and pin cards or cash. Unfortunately have founds machines that will only take coins. That is a pain.

@Lee, I guess you confused me. I was referring to being able to buy with cash, but at a counter from a person, not from a machine and I thought you were saying that couldn't be done, that there were only machines. Thanks for clarifying.