I have to admit that until last week, I never read the Park city improvement Civilopedia entry correctly. My mind only processed the "reduce building pollution by one" part and totally ignored the "limit building pollution to one" part. Since i now realize the actual abilities of the Park (and have played my first game understanding its abilities), I think some adjustment to the pollution reducing improvements is needed. As currently configured, the ability of the Park to limit building pollution to one totally obviates the need for the Labor Union and Recycling Center building pollution mitigating improvements. The Park is cheaper, earlier in the tech tree, provides culture and is more effective. The Sewage Treatment Plant and Mass Transit System city improvements still retain their viability. The Sewage Treatment Plant can reduce to zero the one building pollution left over from the Park (although I think it nominally reduces two pollution, more than it needs). The Mass Transit System is the only improvement that addresses population pollution. With the current abilities of the Park, neither the Labor union nor the Recycling Center city improvements have any value. Perhaps if the Park either only reduced pollution by one or limited pollution to no more than 3 (or possibly 2) the other improvements would gain some measure of viability. Another way to improve the viability of the Recycling Center may be to reduce its maintenance cost to zero or, if possible, make it negative. To me, it is reasonable to assign the Recycling Center a negative maintenance cost, if that is even allowed, or a zero maintenance cost if it isn't, on the grounds that the sale of the recycled material would at least offset if not more than offset any operational costs. Even with the zero or negative maintenance cost, it may need the "limit building pollution to 1" flag of the Park or have the ability to also reduce some population pollution (if that is even possible). The Labor Union is probably not viable with its current abilities. But considering that labor unions typically improve working conditions, adding a happiness modifier to the Labor Union improvement, in addition to or instead of the pollution mitigation would improve its viability. In all honesty, I never developed a mental rational as to why the Labor Union improvement reduced pollution, I just didn't see the connection. Increased happiness or reduced war weariness or both make logical sense. Oh and on another point about pollution, I don't think the AI ever builds pollution reducing improvements. Have you noticed that? Maybe other tweaks to pollution are required because of this blind spot on the part of the AI.