black objects when rendering scene (BI) when I try to render this scene I have everything black. I've used Mineways to export the model.  I think it is a light issue because if I add a sun lamp it becomes colored, but only from the direction of the sun.  The rest is all black like nothing reflects any light. What is the correct way to have a realistic illumination in this case?

Here is the .blend file.

Edit: adding environment lights there are no shadows but light works: https://www.dropbox.com/s/wxtodq863iascje/progetto2.blend?dl=0

I did a lot of tries, and seems that if I put an ambient occlusion or environment lighting in the world properties panel, it is rendered properly, but in this case I have light from everywhere and not from a sun, so no shadows are rendered.
Your scene lack environment lighting, meaning that the shadows will be black, giving your scene that odd look. Furthermore, due to the import-export your materials are not textured. What you need to do is to first, add environment lighting, and then second, add textures/better materials