We are going to be driving from Amsterdam to Kiel. what is your advise for stops along the route? it does not mater how late we arrive to Kiel - our cruise is next day. Thank you!

I would absolutely give Hamburg a visit. Especially the center with the beautiful lake. After you will enjoy the peace in Kiel a lit more .

Innenalster is the lake in the center called.

what about Bremen?

Amsterdam - Untrecht - Groningen - Bremen - Hamburg - Lubeck - Kiel

Utrecht - sorry

@Aramis: Good luck with that. Driving time of that route: 7 hours (not counting stops and the endless Baustelle on the German Autobahn around Bremen, Hamburg and Lubeck). If anything I would vote Bremen. It has some historic medieval buildings and a good atmosphere.

Lübeck is a unesco site, but a bit out of the route.

Hamburg was bombed to ruins in WW2, there's not much left from times before than.

It's actually about 8 hours driving,

They were suggestions of places worth stopping along a general route to stop, not a defined route. I guess I could have left Amsterdam off to avoid confusion, but nobody stops in 5 cities in one day on an 8 hour drive, do they?

Lubeck adds about an hour from a direct Hamburg Kiel route but since you are dismissing Bremen and Hamburg it's probably very doable if Utrecht and or Groningen don't excite.

I didn't know it was a pre WW II history trip the OP was undertaking.