Cities

 Pictures:
https://www.londonslostrivers.com/ vg

https://www.undercity.org/ vg

        https://www.npr.org/2011/01/02/132482428/into-the-tunnels-exploring-the-underside-of-nyc

https://www.kuriositas.com/2011/07/fleet-londons-underground-river.html vg

https://www.gettyimages.ca/search/2/image?family=editorial&phrase=sewer

https://wearesouthdevon.com/the-fleet-torquays-subterranean-river/

https://victorianweb.org/technology/bridges/32.html

"Where Fleet ditch, with disemboguing streams,
Rolls the large tribute of dead dogs to Thames."

https://www.kuriositas.com/2013/10/the-red-menace-anti-communist.html int. 50s contemp posters

https://en.wikipedia.org/wiki/Catacombs_of_Paris 6M+ buried - a wall made of bones

    "Arrête! C'est ici l'empire de la Mort" 

       built directly under the streets so can't build tall buildings there

https://en.wikipedia.org/wiki/Les_UX charged in court for restoring the Pantheon clock '

https://www.christopherfowler.co.uk/blog/2014/08/20/london-corners-underground-waters/

    gold fish in the river Tyburn

https://en.wikipedia.org/wiki/Mole_people live in the tunnels and subways