I'm sure a lot of you have played this, but this thread is for those who don't know about it.
This is my personal favorite Half Life 2 mod. It's really beautiful, would probably be described as art by most people. The writing is amazing, the music is incredible and the atmosphere is really immersive. It's been over a year since I've played this (came out 2008) and the experience has still stuck with me.
This has to be played, you will thank me.