A thought about natural wonders - Why do they give money as soon as you see them? Sometimes on the first turn of the game. In pre-historic times, they maybe in awe of the wonder (so give them culture points [not to many - but maybe an extra point every X turns], not money). They do not even have money then. Then give them some money in say the Classical era, when they appreciate what they have and people flock to see the wonder. Generating income.