Originally the plan was to set the scene on top of the buildings but that quickly changed after I realised the scale of the project it would need to be.
I start by gathering references into a Miro board (this should stay up for a good while: https://miro.com/app/board/o9J_kvuLQ5s=/) where I can break down images, highlight aspects and mark notes and then carry relevant parts over to my Pureref for when I'm using specific references.
Blockouts done in Blender, I get the shapes, switch between Blender and Unreal as I work out the lighting and then start breaking the scene down after I know what I want including modular aspects and props. I find it important to do it this way because I can constantly be making tweaks and changes.
When it comes to reference gathering the probably most important source I found was in fact Google Earth; it had honestly skipped my mind that was a thing for a good few years now. Google and Pinterest are okay but Google Earth allows you to get unaltered references for buildings and the materials that go into making them as well as see the same make-up for a building across multiple instances.