Okay. I have played this game and I really like it...but I have one question that bugs me.
The general rule for wonders is that you use them once (per era) and then you turn them face-down. This makes complete sense for all of the wonders, except one, because they all have just one effect.
The Hanging Gardens of Babylon has several effects. First, "If you suffer losses when rolling the Conquest die...you don't lose any Population counters." This is simple, if you use this once, you turn this wonder face down and you cannot use this again.
But this wonder has two more defensive effects. Specifically, the card states, Cancel the effects of "The Great Wall of China" and "Tenochtitlan" cards.
So, how does this work?
(1) Do you have a choice of which of the three powers you can use (cancel the bad die, cancel the Great Wall OR cancel Tenochtitlan)? When you use any of them, the card goes face-down?
(2) Only the first effect (cancelling the bad die) forces the card to be turned face-down and so while it is still face-up, you always get the other two preventative effects?
(3) Only the first effect (cancelling the bad die) is limited to one use and the other two preventative effects are always present?
I have played the most conservative view so far (#1) but I think (#2) makes more sense. #3 seems very powerful but it may help to balance out other matters with 4 players?