Le pacte des loups: Director's Cut (2001) directed by Christophe Gans
Brotherhood of the Wolf probably doesn't qualify as a horror movie, but a film about a "beast" terrorizing a village in pre-revolutionary France gets pretty close. It's a beautiful movie, with mist-covered French countryside, a castle and elaborate period costumes. I found it easy to fall into to film, which was helpful given the 2.5 hour runtime.
At the worst, my only complaints would be about the kung-fu fighting and one of the plot points. The fighting -- though very well done -- doesn't really feel like it fits in the 18th century setting. I don't think people generally did lots of flips and roundhouse kicks when brawling back then. I could be wrong. It all looked cool, anyway. Also, one of the plot points towards the end of the film is bit repetitive / manipulative. We're made to think that Marianne has died, leaving Grégoire alone. This happens shortly after we're fooled into thinking Grégoire has been poisoned in prison. Once is fine, but twice in the same movie is pushing things.
Other than that, the film is pleasure to behold. (8/10)