How do I make floors opaque between levels

[nbh707]

I am making a house with a courtyard in the middle. In order to see the difference between the open and closed areas, I want the ceiling of the first level/floor of the second level where it is not open to be opaque when I view it as a virtual visitor. How can I achieve this?

[Puybaret]

I think you should select the 3D view > Display all levels menu item.