The prison camp set in this movie was built (and still stands) at Deer Park Heights outside of Queenstown, New Zealand (where much of the filming of Rohan was also done for The Lord of the Rings: The Two Towers (2002)).
A large part of this movie was filmed around Queenstown, New Zealand. The prison camp set is still standing, and can be viewed at the Deer Park Heights nature park outside of Queenstown.