Why do i can't open an exported .obj file on Unity?

All I did was I opened blender, created a plane beside the default cube. I scaled the plane and used Nurbs to form some sort of curved road and I applied the modifier then I exported it to obj and 3ds.

But when import it from Unity, the cube was there but the curved road was not in there.

What is wrong?

Are you going to supply your .blend, .obj and .3ds files ?

Yes here it is:


curve road.blend (547 KB)