BUILDING21

The construction of megalopolises and underground cities in Chicago shows their usefulness.
We can build a bunker, or an underground house. What is absolutely certain is that there is a lot of free space under the ground.
Also, it's always warm under the ground, getting warmer with each meter. Energy savings in heating, protection from harmful emissions, creating a microclimate.
it is still difficult to build a house a kilometer high, but you can build a house 50 kilometers high under the ground, now there are high-speed elevators and all the necessary support systems. there is a lot of free space on the planet, so it makes no sense to build too deep, for the average resident 2-3 floors deep into the planet is enough