Reviews I've seen of this film didn't rate it very highly, but I feel it was underrated. The story, set in the subterranean network below Moscow (which is actually for real, though perhaps does not contain any alleged gateways to hell...), is atmospheric and eerie, leading you further into the depths along with the characters. The plot is not explained in words of one syllable, or telegraphed till there are no surprises at all, but you can catch the drift and understand what is happening if you pay attention. Don't wait for massive outbreaks of gore or expensive fx, there are none; this one, like The Orphanage, relies on shadows and startling moments of unearthly clarity to create its effects. The ending does leave some matters open to speculation, but for me that just makes it all the better. Suspenseful and thoughtful.