Originally posted by Grailer:

big cities was not intended for this game , They intended for many smaller bases linked together by portals .

But it's not just cities. I have a house that barely fits a bed, a workbench, and couple chests. Additional stuff like the furnace is lining the walls on the outside, with minimal teraforming around it and a modest carrot patch. And even that makes thing about 20fps lower when I'm there.