When you adopt a policy that multiplies the production of a specific type of building or unit chopping causes too much production overflow. You can pretty much build districts in 1 turn. How: - adopt the production modifier policy - build the cheap building or unit to 1 turn - chop - select an expensive new project (district, wonder) If the ancient walls (limes policy) need 10 more production to finish, chopping a forest for 100 production will overflow 190 production. The correct behavior would be to overflow 95 production (5 to finish the walls, 95 for whatever else). Applies to: walls, galleys, heavy chariots, archers and so on. Also works for jungles. Most likely also for harvesting. I have not tried to select yet another multiplied project in a row. (galley, galley, expensive project) If chaining works it might be possible to 1 turn build anything.