train connections in Belgium and Cologne

You might try to give us more specific information (train numbers, times). The only night train connection I could find from Prague to Paris had a one platform, half hour change in Köln, but that was from the night train to a Thalys train. I would think that if you were limited to the luggage you could carry in one trip, you would be fine. If you have to make two or more trips, you'd be in trouble.

As far as I can see, the night train from Prague gets into Köln at 6:14 on track 6. The next ICE leaves for Brussels at 7:42 on track 7. That's a cross platform change, but you have 1H:28M to do it. That ICE gets into Brussels Midi at 9:35. There is a Thalys leaving the station at 9:37. Unless that is a cross platform change (they don't give track numbers for Belgium, you'll never make it. Next Thalys after that is 8:15 10:15. That change would not be a problem.

You've got it Lee. We are on the 10:15 after all so all is well. I was panicking unnecessarily. It's going to be a long night. Hope there is somewhere pleasant to sit while we are waiting at Koln and Brussels. We are not young. Do you know the stations at all? We had hoped for the Koln to Paris Thalys but when we were booking it was not available due to track maintenance so we booked alternative just in case. Thanks for all your efforts.

I've been in two stations (or one station twice) in Brussels, but can't say I know them. In Brussels you will only have 40 min between trains, and although that's enough time, by the time you figure the track number for your outgoing train and go there, you might not have too much time to kill. I changed trains in Köln in 2008, but I did some study in advance as to where things were. (Instead of a quick change of trains, I built in a two hour stopover on my Sparpreis ticket and had lunch in town and looked into the Dom.) In Köln you might have an hour and a half. This is the layout of the Bahnhof in Köln. In the lower right corner (south) is the exit for the cathedral if you want to take a look inside it. I imagine it will be open. Just inside the door is a blue square saying "Gepäck Center". There is a check room (Gepäckaufbewahrung) where you could leave your luggage for an hour. There are also automated locker kiosks outside the Reisezertrum on Passage D. They're high tech. You put your luggage in any kiosk and it takes it to the basement, then delivers it to any kiosk when you're ready to retrieve it. If you have been in an eco sleeper or a couchette, you might want to avail yourselves of the pay showers (blue rectangle) off of Passage E (top of plan). Of course there are plenty of places to eat if you didn't get breakfast on the train. There is a lounge. It might only be for 1st class passengers. It shows over the red area (DB Reisezentrum) but the note says it is at track level, so you might have to get to it from platform 1. There is an escalator right outside in Passage A.