Hamburg it is ! The AC/DC reference was that the cult club F.C. St. Pauli (German second division) always run out on the pitch to the playing of this. The national border was with Denmark (for about 80 years Altona and the whole west of the present city where part of Schleswig Holstein which was Danish). The 4 churches were the Danish, Swedish, Norwegian and Finnish seamans churches (all in the AdmiralitätsstraÃe). And.. it has more bridges than any other city in the World and the underground marathon uses the old Elbe Tunnel. Over to you.