Stayed first night @ Cologne-Mullheim HI express, traveled a bit near the train station when I was done with my meetings.
I really liked the luggage storage @ the train station!

Took the train to DUS Hbf and stayed in the HI close to it, walked to the old city area - man, you DUS guys know how to party - the area was PACKED with people going out, eating, drinking and generally having some good time.

Ended up taking a taxi in the morning to DUS, spent some time in the Biz lounge in which I declined the many alcoholic temptations so early in the morning...