This is just taken from my Thomas' War mod, turingmachine asked if I could separate it.
Basically it does two things. The first, once built, will allow you to contact and thus trade with all other civs on the map regardless of if you actually met them (this is actually the effect of the Tower of Babel wonder in CivRev but I didn't want to make a Tower of Babel). Note this is with all civilizations, not between, so only you will gain contact with everyone not everyone else with everyone else (like the UN does). Secondly, considering Civ counts walls, the Great Wall, and castles as basically espionage buildings, I thought the Ishtar Gate is an appropriate choice for the missing commerce per religious building; espionage.
All the python is labeled and searching for "Ishtar" should find all the changes.
I recommend downloading winmerge to help combine the files.
XML, python: me (tsentom1)
Building: Not sure, is in the Greek World vanilla mod
Wonder Movie: Arian
The Ishtar Gate Wonder (XML+Python) 2016-10-05
The Ishtar Gate Wonder (XML+Python)