Largest wastewater treatment plants

https://en.wikipedia.org/wiki/List_of_largest_wastewater_treatment_plants

https://www.mswmag.com/bytes/2025/03/the-most-complex-sewer-systems-in-the-world 

https://caleywater.co.uk/blog/2024/08/29/the-engineering-marvel-beneath-tokyo-the-worlds-largest-sewer/

 https://www.zoomdrain.com/blog/2022/september/the-worlds-largest-sewer-is-in-tokyo-and-its-unb/ 

https://www.slate.com/blogs/atlas_obscura/2013/05/17/g_gans_the_world_s_largest_drain_sits_below_saitama_japan.html , https://www.youtube.com/watch?v=b7jIqru1Nzo

https://www.reddit.com/r/interestingasfuck/comments/j3y95z/underneath_tokyo_is_the_worlds_largest_flood/ 

https://thedigitallabyrinth.blogspot.com/search?q=sewers