I was a little dubious going here as to whether it would be worth a visit, or even its place on the World Heritage list, as there are already plenty of other examples of Roman Theatres included. However, I was shocked. The theatre is magnificent. It is absolutely huge and almost completely intact.
I have been to a fair few roman theatres, including quite a few in the area around Orange, and this is probably the finest I have visited (although the one at Dougga in Tunisia probably has a better location). The feature that makes this different to all the others I have been to is that the stage wall has remained standing since being built, and there are still some decorations on it. There are also the remains of a roman temple right behind the Theatre.
The Triumphal Arch (pictured) is also well preserved, and the friezes are remarkably intact. It is only a short walk up to see it, and it is nice to see but perhaps only worthy of its place on the list in addition to the Theatre.
Orange itself is nothing really spectacular. It is nice enough, but apart from the two sites there is not a whole lot more to do. We spent an afternoon here and that was enough time for us. It is only about 15 minutes by train from Avignon and is a nice way to spend a couple of hours.