I'm visiting Maastricht in april for 8 days. Will spend a day in Luxembourg City, but I need help deciding where to do an overnight visit. I'm considering: Trier or Heidelberg Germany; or somewhere in northeastern france (eg. sedan, metz, or ??). Your ideas would be a big help. Thanks, dank u, danke, merci...

We found Trier quite interesting - esp the Roman remains and ruins right in the middle of a typical German town. But - we were on a road trip - so don;t know about transit to and fro for you.

Hello,
Depends on what you are seeking Trier is a cool town with some great Roman ruins and Karl Marx' house...Heidelberg, of course has the famous castle..and a cool town in itself....if I had between the two....go for Heidelberg

I vote for Metz.

How about staying in the Netherlands and visiting Groningen and/or Assen - see the terracotta army.
Or for something different Texel or one of the other Wadden Islands.

This past September, we stayed in Bernkastel-Kues on the Mosel River and did a day trip to Trier and to Echternach, Lux. Photos of both can be seen on webshots:

http://good-times.webshots.com/album/561038806XxDcvw

I would highly recommend Aachen as a day trip if you have never been there. You could go to Brussels, Gent or Brugge for an overnight