Synopsis:
The stupidest tourists you've ever encountered in your life go urban spelunking in some defunct Berlin underground tunnels.
Review:
If you ever write a screenplay about this subject, for fuck's sake, spend a few hours researching what it's like to go caving. Things like maps, compasses, first aid kits, basic climbing gear, etc. that get distributed to more than one person spring immediately to mind ... you know, just in case the dude with all the supplies falls down a hole and you have to get him. Secondly, your tour guide that takes people through tunnels that he describes as "frequented by criminals" ought to be packing a better weapon than bad negotiating skills.
I assume the director went down his Universal Slasher Checklist:
Inability to finish off the villain when he's face down, unconscious, defenseless, and at point blank range with all kinds of blunt and sharp objects located near him? Check. Twice.
The inevitable pause a character makes right as they look over their shoulder before they're about the escape? Check.
Unnecessary and easily avoidable actions which lead to the demise of one or more characters? Check.
Verdict:
Just fucking bad. One of those suspense/horror flicks that drops the ball on fright and does it in such a dumb-ass way that there's no salvageable entertainment value.