I got a bit confused when I read this sentence:
Nach der Apfelweinkneipe sind Christa und ich in der Frankfurter Altstadt spazieren gegangen.
Since the noun Altstadt is feminine and we're using the verb gehen with the two-way preposition in to describe we're going to somewhere, shouldn't Altstadt come in the accusative case?
I think in this sentence it'd be ok to use the dative case with another verb while using in:
Nach der Apfelweinkneipe machten Christa und ich einen Spaziergang in der Frankfurter Altstadt.