I suck at introductions so I'm not even gonna try. This movie is very good. I like it. If you are interested in Horror cinema or just visually intriguing films in general you need to check this out. All right then, on with the specifics.
The plot is easily summarized. Suzy Bannion is an American ballet student in Germany. There a bad goings-ons at the academy and she must investigate and defeat the evil to survive blah blah blah. None of that really matters. Even the staunchest defenders of this film often admit that the plot/script/dialogue are not particularly inspired, and frequently kinda lame. I tend to agree with this belief, but as I said before, it doesn't really matter. However, contrary to what many people say, I didn't find this film to be the least bit confusing. I'll admit that not necessarily everything that occurs makes a whole lot of sense, and that some things are shown which are not terribly vital to the plot, but it's hardly difficult to follow. The acting isn't so great either, with the protagonists coming off a bit flat much of the time, and the antagonists overdoing it, particularly the whacky Miss Tanner, whose got a weird female concentration camp commandant thing going on.(or maybe I'm thinking of Madame Blanc, I get the names confused. If you see it you'll know who I'm talking about.) Still, it's a masterpiece visually.
When people talk about this movie they almost invariably describe it as being nightmareish. I don't really care for this description, because it exaggerates the surreality of the film. Visually, it isn't hyper-abnormal, it's really just surreal enough to seem just beyond the bounds of reality, so that nothing in the film seems quite real. This is particularly effective in the Academy itself, which mixes stately, classical looking architecture with extremely garish and tacky, extremely 70s-ish decoration. The night/horror scenes are all the more effective, with natural coloring being essentially abandoned, with everything then being bathed in eerie colored lighting. The two most prominent colors are blue and red, with a smattering of green now and then. On the whole it is startlingly eerie, and can add immense power and atmosphere to scenes where essentially nothing happens. A good example of this comes when they are forced to sleep out in the ballroom due maggot infestation.(which is itself an example of a creepy thing that happens that has nothing to do with anything) Nothing really happens here, but it's bathed in an intense, absolutely hellish red light which gives it immense power. To accompany these visuals is the much-hyped score by Goblin. It is extremely effective, though occasionally weakened by the odd cheesy synth line. It's mostly eerie keyboard lines playing menacing, repetitious melodies, thunderous percussion and random, rumbling bass overlaid with demonic voices whispering and howling. It also gets points for sounding like actual music, rather than the auditory exclamation points that most horror films provide you with. Despite all this, this movie isn't all that scary, but it's pretty eerie and atmospheric, and is just damn cool.
The film suffers slightly from starting off too well, so it's unable to maintain it's level of excellence, and suffers from a rather anti-climatic ending. Still, the opening scenes of the film are absolutely great. Suzy's arrival in Germany during a fierce storm sets the tone for the film, and establishes most of the visual motifs. It is perhaps the most surreal portion of the movie, with the heavy rain obscuring most everything, and particularly random seeming uses of lighting.(The weird forest they pass through is especially cool) The first murder scene, which is early in the film, is easily the best of the horror set-pieces. Although it isn't really all that gory it's a truly brutal scene and ends with some genuinely horrific imagery.(I'll admit that the effects are dated, but they still work very well in this scene, imo) The other horror scenes are reminiscent of the first, indoors, with the use of phony looking set decoration and colored lighting, with one exception. It takes place out in the open, and the normal colors are abandoned, instead opting for utter blackness and plain white and grey coloring on the surrounding, neo-classical architecture. It's also got some great, Leone-esque staging and camera work, as it drags the scene out as long as dramatically possible, alternating between extreme long-shots and extreme close-ups. It's a great scene (other than some dated gore) which is made all the more effective by how it contrasts with the rest of the film.(I should mention that despite the supernatural trappings of the film, the killings are generally done manually, with slasher-esque staging and methods. This film has witches, but they ain't much like what you usually see.) As I said before, the ending isn't so great. It's a bit abrupt, and doesn't show us anything we haven't seen before, but just re-iterates old motifs in an inferior manner, and suffers from some bad acting on the part of the main antagonist.(Well, now that I think about it, it does have one great scare, which is unexpected and unlike what we've seen before, but overall it's just not nearly as good) Also, there's a scene with a bat which is unintentionally funny. That bat's just so damn adorable.
Well that's about it. Some flaws, but it's a horror masterpiece anyway.