Without lighting the scene looks quite dark and dull. For architectural scenes and environments, you probably need a sun-like light source. We will add a Directional Light by navigating to GameObject | Create Other | Directional Light. This is a light source that emits light in one particular, parallel direction. Its position does not matter.
Press E to activate the Rotation tool and drag the colored circles of the Rotate Gizmo to point it downward, as direction is very important. This can be seen in the following screenshot:
While we said that position doesn't matter, it often makes sense to place the Directional Light slightly above the scene, with the rays pointing towards your design, as a visual clue for yourself.
You can adjust Color and Intensity to your liking. Slightly yellow with intensity between 0.5 and 1 is a good starting point. You can also activate the Shadow Type, which enables real-time shadows. Beware that this can be computationally expensive. Further setup...
