I looked at a photo of the downtown of a city with all its many skyscrapers, and the thought occurred to me that this collection of tall buildings has a very high surface area to volume ratio(see note) and that this is the least effective at keeping the hot or cold climate out. Just to keep the skyscrapers livable requires a lot of insulation and a lot of HVAC.
My thoughts moved to how to remedy this. I thought about the space between two large buildings. This outside space could be enclosed to keep out the cold or hot weather. This would save both of the buildings some of the cost of keeping the rooms air conditioned. One disadvantage would be that all windows on those sides would lose the view they had. But some of the enclosed space could be used for growing plants year round, which would help the views. Some changes would have to be made. The structure would have to be self-supporting, so no additional weight will be put onto the two buildings. The structure could cover only part of the empty space between the two buildings. The space inside of the structure would not have to be used for human habitation. The structure’s outside walls would be insulated to keep out the weather outside. This would reduce the heat losses through the walls of the two buildings.
Some buildings are separated by an alley or small side street. The structure could be built over this alley, leaving a tunnel for passage of vehicles. Currently there is some concern about exhaust fumes from vehicles filling up the tunnel. But in the next 15 years, maybe sooner, most vehicles will no longer use fossil fuels, so the emissions from these new green vehicles will no longer be toxic.