At this point, some areas are still too dark, so we need to fill them with light.
Lighting the scene using "bounce lights" and overhead "skylights": The front view of our bridge looks unnaturally dark, and not in harmony with the walls because there aren't skylights targeting it yet (At this point, we 've only got "skylights" on right/left sides.) This time, a simple spot is placed at a distance to fill all frontal areas. To take more control of lighting exposure, I used a lineal falloff and soft shadows using opacity only at 50%; this produced a more "filling" light.
Note that the bottom area of our bridge doesn't show enough bounced-light while sunlight looks high on the floor. To remedy this, a simple light without shadows is placed under the scene to fill bottom areas with "reflected" light. This simple light uses a 15% value.
Now is when I apply the overhead "Skylight":
In total three omni lights with falloff are placed in a medium-top area of the overall scene. Two omni lights with a 20% value are placed at front and back of the bridge, at a medium-top position. The third light, with a 35% value, is placed at the top, higher up, but toward the front since only this area is visible to the camera.
Finally small details to improve believability: Because the walls at the back of the bridge fade to open space, more Skylight must appear on it. To "overexpose" the open area I used a pair of blue spots with a 30% value, targeting the walls at top, and an omni yellow at 25% value with falloff on the open space between the end and rear wall.
