Yes, a directional light for the sun, and an environment override with a ramp for the sky.
Render time ~1h30 by frame in 4k, all in proxy (with some objects from Houdini) and textures in exr tiled/mipmapped.
First, we baked a irradiance map on 1 frame with “use camera path” setted, on a computer with 45giga ram.
After, we rendered on the renderfarm with computers which have 24giga ram.
For the city, like 3 months.