There are a lot of people who live indoors almost 100% of the time in the winter in northern climates. A lot of the larger northern cities have underground walkways between buildings with subway access etc. No one wants to even walk across the street when it's 40 below. :)
I expect that designs for 'permanently underground/inside' cities would need to include some high-ceiling park-like areas with some bright UV lights, and other considerations, but that sort of thing seems pretty doable. Whether it would be enough to maintain a population's mental heath I guess would need to be seen, but generally speaking I think humans are a pretty adaptable bunch...
I expect that designs for 'permanently underground/inside' cities would need to include some high-ceiling park-like areas with some bright UV lights, and other considerations, but that sort of thing seems pretty doable. Whether it would be enough to maintain a population's mental heath I guess would need to be seen, but generally speaking I think humans are a pretty adaptable bunch...