There was also a bug at some stage where the game would crash when it tried to render the earth walls building in barbarian or Neanderthal cities, and changing SHOW_BUILDINGS_LEVEL to 0 would fix it.
Setting to 0 speeds up graphics when scrolling around using map paging, as it doesn't have to load and render as much stuff, good for bad graphics cards like mine. Of course it makes cities look all the same.