What are your best places to sit on the Rhine (near the center of town)?

I'm going to Köln tomorrow with a few friends and was wondering if any of you know some sweet spots along the river bank, preferably some spots where you can socialise with others as well. We plan on bringing our own booze so cafés are not necessary (No littering, I Promise)

We don't plan to stray TOO much from the Hbf (Central Train Station) since we have a train back to catch!

Hope you can help a tourist out here, Many thanks