As the picture shows, the bottom part of the hospital is covered with shadow and I don't know why. The face normals are not flipped. This happens in both solid view and rendered view.
What causes these black shadows?
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You use smooth shading on a non-manifold mesh, which does not work properly.
Another option is to assign hard edges, e.g. using the Edge Split Modifier. This way some edges are shaded flat and others smooth. Flat shading works with non-manifold mesh the same as with manifold mesh. Because in this case the non-manifold spots have large angles, shading problems will be solved.