@Frank you are right. This was intentional as the idea behind was to simulate a sort of maquette.
@Hutton Basically all models in scene are low poly (tree leaves are just planes) except vehicles and nearby mountains, which were sculpted a bit.
All the materials are procedural, I abused largely of mix material, dirt node and noises, specially in ground and mountains.
Water was just planes with noise and a little of Hot4d for the closer parts like the river.
For the illumination I used a HDR image mixed with a Sun light.
The sky background was just painted in post.
*Finally the client liked it so much that he ask me to render a 11x8m image (thanks tiled camera), so I was very happy to have invested heavily in the optimization of the scene
Win10x64Pro || C4D || i7 2600k || 32GB DDR3 || 1x MSI Twin Frozr II 1GB (Display) + 1x EVGA 780Ti 3GB