UTL is about exploring past, present and future urban technologies in science and fiction, etc...
For some, Coober_Pedy just might be the epitome of underground_living.
https://www.sciencetimes.com/articles/45520/20230821/humans-live-underground-escape-extreme-temperature-earthscrapers-potential-solution-climate.htm
https://www.energy.gov/energysaver/efficient-earth-sheltered-homes
https://jfdatalinks.blogspot.com/search?q=living+underground
https://therabbitportal.blogspot.com/search?q=Coober+Pedy