Wiring for CD Changer 96 Estate Wagon

I am thinking about adding an aux RCA adapter to my wagon via the CD changer harness. The car did not have the CD changer option install when purchased, but I've been told that the car was prewired for the changer so that the dealer could easily add it. If this is true, does any one know where I should look for the wiring termination? I have looked in the spare tire well and do not see anything obvious.

I don't know about any factory harness, but I've seen changers installed in the lockable compartment on the driver side at the back of the car.