Terraforming tricks

When mt game is advanced and you don't plan to expand further I tend to make fortresses on the border of my empire and got reeeeally pissed off when a howitzer came and blasted my poor defenceless mech inf, so what I do now is terraform a "trench" three squares deep into hills. It take time but it really slows your enemies down.

[My Wife Hates CIV]

An engineer can transform plains into grasslands and than grasslands into hills. This can be done on a fortress or in a existing city. Just move your engineer on to the desired sqaure or into the city you wish to change. Than look at the orders menu. Of course more than one engineer will speed things up.

I think forests can be changed to grasslands and if you need extra defense fast plains can be changed to forest. +%50 for forest and +%100 for hills on defense.