Upgrade on the quarry - To make the most of the quarries remember this guideline: Depleted quarry on upgrade gives 50,000. New quarry (never mined) gives 250,000. Currently I have six quarries and have upgraded one depleted quarry. I have put all my workers into it which only utilizes 15 workers at this time. The plan is to upgrade the rest of them before adding back workers which will yield 5X more stone. For new limestone mounds after expansion, I will upgrade quarry giving 250k stone then workers added to it. Upgrade cost 8k gold with zero time to build.