Also, you can search for wonders in past posts:
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Before I begin, let me clarify what I consider wonders in a game. For me, wonders represent not only physical monuments, but also achievements and concepts that trigger great changes. Having said this, here are some of my ideas, in rough historical order.
(note: these ideas are part of my CTP2 modification project that I have yet to resume - I have prerequisite advances and obsolence advances based on new advances I have thought of)

Grand Canal
Why: The Grand Canal was a major engineering achievement of ancient China that dramatically increased water trade between the Hai, Huang, Huai, Yangtze, and Ch'ien-t'ang rivers. The immense 1,100 mile long canal was begun in 300 BCE and was completed in 1200 ACE.
Game Notes: gives equivalent of one free merchant in every city of host civilization

Aryabhata's Mathematical Treatise
Why: Aryabhata was a mathematician of ancient India, who lived during the time of the Gupta empire. His Mathematical Treatise expanded upon astronomy, algebra, and trigonometry.
Game Notes: gives equivalent of one free scientist in every city of host civilization

House of Wisdom
Why: The House of Wisdom was constructed in medieval Baghdad in 832 ACE. This building was a center for preserving the knowledge and concepts founded by ancient Greek civilization. Without the Arabs, Europeans would not have progressed as they have done.
Game Notes: gives host civilization and all other civilizations two free, Middle Ages advances

Luther's 95 Theses
Why: Luther began a revolution in Christian Europe when he presented the Church a theological as well as an institutional challenge in the form of his 95 Theses in Wittenberg, Germany in 1517. Thus, began the Religious Reformation.
Game Notes: Clerics of host civilization and all other civilizations have 100% success rate for all Special Attacks/Abilities

The Copernican System
Why: Copernicus wrote the book titled "Six Books Concerning the Revolutions of the Heavenly Orbs” in the 1540s. When Galileo later proves Copernicu's theory, there was definitely no turning back to the solar system that was conceived of having the Earth at the center. Thus, Copernicu's work laid part of the foundation for scientific inquiry.
Game Notes: gives one free University in every size 10 city of host civilization, and all other civilizations

Hey MrFun, looks like your wish in principal is being honored, more wonders. Specifically the Grand Canal. Good now I won't have to waste a city in Panama just to get a canal and be stunted by a Babylonian city in the wrong place to make the Suez