lived around Cologne for 3 years, if you head for the cathedral in the centre everything is with in walking distance, bars restaurants & clubs, a nice place to have a wander and partake the local beer which is excellent, enjoy.
Go and see Gerhard Richter's stained glass window in the cathedral. It's my favourite piece of art. I can sit and gaze at it for ages. Pick up the leaflet which explains the thinking behind it and what it stands for; not only is it joy to look at it also stands for so many things I believe in and touches a few elements of my life. Wonderful.