Tropico 4

The Diamond Cathedral unlocks ~1988 and costs $40,000 so save up some money before 1988 and build it as soon as it unlocks. If you don't have enough money to insta-build it set the build priority to max and send your avatar to the construction site to speed up construction.

There is a way to do this which does not require waiting until 1988 to unlock the building. On mission 6 of the modern times DLC you are tasked with exporting canned goods. Once you have completed this part of the mission you are required to keep the value of canned goods high enough to pass the level. There are several tasks that appear which higher your canned goods index. One of these is from father Esteban who asks you to build a diamond cathedral. This automatically unlocks the blueprint for it and is available in the 1970s. Doing it this way comfortably gives you time to save money for the building and to construct it.