On turning 45

I'm treating myself to a trip to Cologne this weekend. I aim to do very little. Perhaps swim in the hotel pool and sit and enjoy the atmosphere at Max Stark's. They serve a black pudding dish (Himmel un Ääd mit Flönz) I want to try. Last week I hurt my knee during a bowling evening with the company, so I won't be walking around too much. I'm staying in the 'Altstadt', but if someone could give me some pointers towards either more modern or more decrepit areas, i.e. photographically interesting?