> Ultra High Density Living is just the most eco-friendly way of living for the masses.

You do not need to go to "ultra high" density, à la Manhattan or Hong Kong.

Once you get to densities of Paris, Stockholm, Amsterdam, Munich, Brussels—in the 50 people per hectare (20 per acre) range—there are diminishing returns:

* https://transportgeography.org/contents/chapter4/environment...

I would not call any of those "ultra high" (though perhaps others would?).

Paris - the city itself - is actually surprisingly high density, almost as high as Manhattan if you do not include the two very large 'Bois' (woods) that are technically part of the city.

I don't know where they get that 50/Ha figure. Paris is more dense than Seoul, with just over 200 people per Ha, or ~20k/km². Figure would actually have been higher at the 1999 date of the cited source, too. The city is (slowly) losing people.

Morgue drawer style housing is the most efficient.

I accept high density cities, but ultra high is misanthropic.

Unfortunately America seems to not be able to get its shit together in how it handles larger cities. Mass transit sucks, life threatening noise pollution, rents are too high, and homelessness abounds while many enter some sort of Stockholm syndrome and think these problems are overstated and defend the status quo. I want to keep living in a walkable high density area but greed, complacency, and outright ignorance destroys what could work for more people.