During ww2 Russians lives just fine in Sewers in Stalingrad, but of course during those years the sewer there probably never seen as little " traffic " of the usual kind.
But yeah the rats are damn tough SOBs, my friend seem to have a larger than usual problem with them this year
People also live fine in storm drains under Las Vegas as i understand it, but with a sudden big rainfall that would of course change.
Some humans are though too, dont happen much here as my country for decades have celebrated weakness, so being weak in just about any way are almost a trend here.
You can get out on your ass on the streets here too, and now you dont have to work hard to end up there, but a decade or 2 ago, if you lived on the street it was CUZ you really wanted to, or was so miserable in some way that you can not handle living in a apartment.
The laws did not change much, but the public safety net under all Danes, well the masks in that net are much larger now making it more easy to fall thru.
BTW back in the old days in Paris ( France ) there use to be tours in their sewers, but at the time they was also something else while the rest of us Europeans was living in our own filth so to say.
But this was going on as late as the roaring 20ties.