Dreamland
Outside somewhere in the world, there was a city named Dreamland. The place was condensed packed with buildings and skyscrapers everywhere, and there didn't seem to be a place of open land that could be seen. A large wall also stood surrounding it around a hundred meters high.
On top of the walls, were several turrets and mechs standing guard day and night patrolling for any danger. Because of these things, Dreamland was considered one of the safest cities to live in. But it came at a cost.
Security was a significant issue, and so was habitable land on Earth. After the war, many of the old cities were obliterated and destroyed. Too much damage had been done. Parts of land gone missing, blown into small pieces, too small for humans to live on.
This was what caused the Humans to create shelters on other planets. It was a lot cheaper than living on Earth, and often many travellers from different associations and families would live there protecting the place.