This is VERY eerie and well worth a watch, I wasn't aware of it, but Valve have obviously done their research:

http://videosift.com/video/Tour-of-abandoned-new-orleans-six-flags

I've been to Six Flags Vallejo (San Francisco) and it was awesome, shame to see another like this (I love rollercoasters is my excuse

More:
http://en.wikipedia.org/wiki/Six_Flags_New_Orleans