I need help to pick my next Centralization

[viking]

I need help, I am on my third centrilzation I have picked mountian with a forst for my first one and the plains the for my second one, I want to farm also defend my self, my questions what to pick the next centrilzation. I have not foght yet and no one has has attacked me also. I am on my 4th Fortress with 2nd Fortification. Tactics [5] Bureaucracy [5] Medicine [6] and building the army every chance I get. So what should I do next.

Viking

[Starbuck]

Plan your colonisations in such a way as to box a mountainous province which provides the best growth potential with the secondary adjacent provinces