In a thoroughly familiar plot, four teens decide to go somewhere they shouldn't for kicks (with the help of a fifth) and end up being hunted one by one.
In this case, they're being led under Berlin to go 'Urban Exploring' into old abandoned tunnels and buildings rumoured to contain deserted and forbidden Nazi bunkers.
Much is made of the difficulty of getting there, and after a long time (and a daft campfire tale) we get a brief and relatively unimpressive glimpse round the bunkers that wasn't worth the build up. It's on the way back out that some excitement starts happening, and 'Armin', a very direct and shabby ex-border guard comes to the group's aid following an accident.
However, Armin isn't as benevolent as he seems, and the characters find themselves in a fight for survival.
So far, so familiar, right?
Well it's not all bad. The actors are good, and have a more interesting and diverse look than usual. Max Riemlet is good as their local guide Kris, and Klaus Stiglmeier is very good as nutter Armin, who torments his victims in some quite inventive ways, including one scene packed with delicious dramatic irony on the subway.
The gore is sparse, but there's an especially nasty and memorable maiming that's quite unusual, and the characters are well-enough portrayed for you to give a damn about them.
As a result, it's a film that feels at once over-familiar and a little fresh, leading to the odd sensation of having seen it all before but also seen a few nice touches thrown in. Not a classic, but worth it for dedicated horror-hounds.