Tips for creating a big city like gta

I need tips before creating a big city like Gta V and I want to know

  1. Gta V city size is 49 Square mi so to create world like this what should be unreal units for landscape
  2. should i use splines over terrain first for designing the roads ,highways and then sculpt the terrain and place buildings and other props?
  3. and other tips

Use Lod’s and instanced static meshes that’s my tip :slight_smile: