An instant cult sci-fi classic very dark and intense that starts slow and builds up to an epic climax.
Definitely not mainstream Hollywood but all the better for it, the acting is superb as are the visuals and atmospherics. Vin Diesel is superb in the role he plays as a notoriously dangerous inmate.
Maybe not quite up to the quality that is 'Alien' but comes very close and is up there with the best sci-fi movies made in the last 10 years. 9/10