Well, if you're calling it Isengard, you should know that the tower is the Orthanc and Isengard is the region around it, closed in by the massive, ancient rock walls which the ents later tear down. On that point, the amount of rock spam is massive, and not too efficient at points, they should at least be pointing to different directions. The background parts are quite good though, nice mountains. On the point of it being Isengard, the river is dammed and jammed away somewhere way up in the mountains, during its time of taint.
So yeah, sure, it's an artist's impression of Isengard, however, that impression has already been set solidly in stone by J.R.R. Tolkien, and we just have to roll with his :/