To extend the conversation a bit....
Blueprints drop for polishing and motivating - but quite low rates.
I think I read they drop for plundering as well - is this right and what is the drop rate compared to polish/motivate.
Helping other people's great buildings also drops blueprints I think - suppose it is a bit early but any thoughts on drop rates here?
Any other sources of blueprints (apart from diamonds)
Great buildings are wonders of the world and supposed to be difficult to earn - I know and approve of that