Here is the point.

Are you forced to build a free unit at your start of the turn ?

The case is : If the army you build is in range of ennemi armies and you know you will lose the figth… Same if, for exemple, you already build your 6 armies and they stand far away, so you can (or have to, that's the question…) only build a scout that will be in range of ennemi armies.

The text : "Start of the turn : Build a figure in the square containing the Hanging gardens for free."

There is no "may" or "can" or "have to". But it's conjugated at the imperative… even if my personnal opinion is to allow the player to choose not build a figure if he don't want to.

I'd have to say that I agree. Even though RAW would suggest that you must, It would be more logical to allow the owner of this (or any) Wonder to choose wether to use the wonders ability or not.

I would read that as optional. At the start of turn, you can use this wonder's ability.

There is a certain Great Person card that gives you a larger benefit for more unbuilt army figures (Turing, I think), so there is at least one pertinent scenario.

Got an official answer about it :

Quote
Hanging garden : Forced to build a free figure or can you abord the ability ?

You can choose not to take the figure.

Lukas Litzsinger

Game Designer
Fantasy Flight Games