Awesome. Just fucking awesome. This proves that you can make a damn good horror movie without some fancy special effects and whatnot.
The movie tells a story of a group of friends who decide to go explore a huge cave. I dont want to spoil anything, but im sure its not suprising if I say that there is something not human in that cave.
There is also a nice amount of gore.
Oh, and you might get a bit uneasy if youre claustrophobic.
http://www.imdb.com/title/tt0435625/