I have a weird soft spot for matte set extensions. So I forgive it, even if the director had a little too much faith in it's realism.
Matte paintings are fine. But when there is a certain level of ineptitude on par with an Ed Wood set, then its not so much art. This one is not so bad, but it could have been helped by just building a rather short inlet portion, and then adding on the matte painting for the remainder of the corridor. It is the change in angle that blows it, when they move the camera down.