If travelling makes you hungry, visit "Oma Kleinmann" (Grandma Kleinmann). She (or her cook) will serve you gigantic cutlets. Make sure you booked seats or, in summer, spontaneously choose a table outside.
Located inside APROPOS COELN, a trendy concept store featuring fashion stores, a beauty salon and a gallery, is Fishermann's restaurant with indoor seating as well as a beautiful patio offering delicious food as well as great drinks (try their wines with the great dessert choices).
For menu see here: http://www.apropos-coeln.de/restaurant/restaurant.htm
Just round the corner from the Hauptbahnhof and grandiosely furnished... looks like it should be a tourist trap but is actually great food and excellent value (and frequented by lots of Chinese people, which is always a good sign).
A place to see and bee seen. Enjoy a decent coffee and sloppy service from a hipster dufus. Has a T-Mobile wifi hotspot, shoddy T1 EDGE/3G reception inside. A decent place to bring your notebook to do some work, meet up to discuss your next startup.
This place is unique in cologne and probably in Germany. Try the "Cag Kebab", marinated lamb grilled on a very large horizont spit over real charcoal.
You can watch the cook cutting slices from the large spit, putting them on a little spit, which he puts on the grill again.
The waiters are exceptionally nice, which makes this a five star tip for a meal.
Incredibly stylish and cute place to be at. The cupcakes are just as awesome as the Oreo-Milkshake for example. A bit overpriced maybe, but as long as you're just going for a snack and not for lunch, this shouldn't be a problem ;)
Very nice hotel with stylish interior. Be sure to like yellow color or explicitly order a room with white glass windows. The yellow greenish coloring of windows in some of the rooms leads to a kind of psychadelic mood. Besides that nice rooms and pictures at the walls. Major drawback: our bathroom had only toilet and shower, the washing basin was in the room outside the bathroom.
Little, very charming café, good food (they are famous for their "blini", a sort of Russian pancakes). Also, most of the guests seem to be creative, innovative people, it's quite an interesting and inspiring place.