I think its the one where I get +1 gold for every 3 or 5 followers. I don't remember how many it is. I like to build a strong economy since it allows me to pretty much do anything towards the end.
This is nice for a tall empire, if all your cities are riverside:
Hmmm, the faster spread chance would be good instead of the +50 faith per GP, but since I'm playing Pacal I get a lot of GPs.
Edit - I had to rename it to something corny like Divine Waterfall
How does that work out for you? Seems a little excessive to me, given how little trouble happiness gives right now in general. Unless you're going for golden ages, in which case, hell yeah! Otherwise, would you maybe want to consider trying for a +growth belief to make more use of that extra happiness.