I'm unsure so I think I'll do both, Ziggurat and Ishtar Gate
Spoiler :
Ziggurat
Ishtar Gate
- Replaces Temple
- Cost: 200
- Maintenance: 2
- +1 Faith
- +1 Science
- +1 Culture
- +1 Food
Ishtar Gate
- Unique National Wonder
- Must have built Walls of Babylon in all Cities
- Can only be built at the Capital
- Upon finishing provides 100 and 100 Culture
- +1 Tourism and +1 Food for every International Trade Route with the Capital