Aircon leaking inside car

[alfaz-di-pi]

I have a problem that when the AC is used, the water taken out of the atmosphere, instead of going down a pipe outside under the car it comes inside to the passenger foot-well. I am assuming that the drain is blocked or dislodged, but my problem is to know where the drain pipe is, and where it starts. Could anyone show me on a photo or even describe where it is. Would it be better to go under the car and poke up to try and clear it. What do you suggest, apart from ripping the AC out.
Thanks
Albert