-Göbekli Tepe was the first temple of humankind.

-It symbolizes progress and the change from nomadic to sedentary living.

-It was the first big building project and therefore a big step in the history of humankind.

Nevertheless it's not well known, so I think it deserves more recognition.

Suggestion for the wonder:

-It could be an ancient (or neolithic if possible) era wonder (first temple)

-It could be a religious wonder and a holy site (temple in real life)

-It could give a discount on founding outposts or cities (or both)(change from nomadic to sedentary living)

 Note: I took the fame category as there was no cultural wonders category.