how to make new terrain "Mountain"

i wish to make this new terrain cause I had lots of problems making Peaks passable, and I didnt manage to enable workers to build mines on Peak terrain, or even enabling city to use any yields from Peak.. so I need help making Mountain terrain that would be something like in Civ3.. and then Peak could stand for realy high impassable mountains (as intended I guess).. anyone willing to do this?

Hmmmm... interesting idea, I nominate you.

Download the terraform mod. It already does all of this and more. This was the very first mod I downloaded on day 1 . I really can't believe so few people know about this one.

Roger Bacon