spamming castle all over feasible?

[pohtato]

Originally posted by Agrajag:
Just wanted to explain exactly what Cainehill meant:
Different terrain types affect the province's "stats", a farmlands province is high on gold income, but low on resources and magic sites, a swamp is low on gold and resources but high on magic sites, a mountain province is high on resources and therefor building a castle in it (and doubling its resource value) will net you more resources to use for your high resource units.

But would having a castle on mountain means the place is more "defensible" like in many other games?