cities and capitals defences

[DukeOfLight]

I observed differences between cities defence:
1) some offers 7 defence for the defender and 0 for the attacker
2) some have 4 for defender and 0 for attacker
3)some have 7 for defenders and 5 for attacker
Capitals: atrough all of them have 4 defence for defenders and 0 for attackers they have different entrecment vakues some have 3 and others 4.
What is the explanation for this? why they dont apprea different...until now i tought that all of the cities have the same value!

[Umeu]

it depends on the terrain hex the city is located on, they themselves dont offer any extra bonusses, only fortresses do (entrenchment bonus)