Originally Posted by
foreigner
Unfortunately Cologne hotels are very full. DUS is same. Day 1 and 2 are free so we could spend time in, around Frankfurt. Days 3,4,5,6 are for business in Cologne.
Any tips on train tickets?
The only way you can get reasonably affordable tickets on a high-speed train is to buy an advance purchase saver ticket (which ties you to a specific train).
It's an awful long way to go. Have you tried looking at smaller places along the Rhine (or elsewhere, for that matter)?