I have to say, I don't understand the hate Petra is getting. Yes, it's very situational, but if you get a good Petra city (Just play a game with Morocco/Egypt/Arabia/Ethopia and you will get it pretty quickly) then you'll see how powerful Petra actually is.
Same here: that single city can be a total game-changer. I think it's because all your desert hills suddenly start producing food, and extra production, and can start building faith with Desert Folklore. Topping that off is culture at Archaeology, and that free Caravan and Trade Route will be gold all game long.
The city that builds Petra (assuming you have a site worthy of it, with lots of desert hills), will be be a food and production monster that spits out money and can spam out other wonders at will. GG.
Chichen Itza - 13
Colossus -24
Leaning Tower of Pisa - 36
Machu Picchu - 20
Neuschwanstein - 31
Notre Dame - 25
Oracle - 24
Petra - 6
Sistine Chapel - 33
Statue of Liberty - 35
Stonehenge - 9
Temple of Artemis - 6
Downvote goes to Chichen Itza. Awesome sounding quote and neat bonus can't save this wonder in my eyes. The AI's steamy not-so-secret love affair with it is annoying as hell, and at the end of the day you've still got to trigger Golden Ages to make best use of it. Still a good Wonder, but it's the bottom of the pack for me.
Upvote for Neuschwanstein again: This thing is worth so much Happiness, Gold, and Culture even in a tall empire. I feel like it's two steps shy of cheating for a wide empire. By the time I have Railroad, the production costs or gold cost for Walls and a Castle in any given city is a pittance. One turn for Walls, a couple more for the Castle, and suddenly that city is up 1 Happiness, 2 Culture, and 3 Gold. Multiply even by 5-6 for a 'Tall' empire and see how it comes out. Now multiply that result by 3 or so for a good wide empire.