Belief is not just a matter of imagination though it definitely starts there. The reality of every single man made structure – large and small – began as an imagining that someone decided they believed they could actually make.
Building belief is really a very individual thing, you have to build on what you have and try things until you find something that works. Two things are definitely true though: Belief is the magic key to your city of dreams and it takes practice, practice, practice to build it.