Just SE of Santiago then, accessed by the lovely Cajon del Maipo, if I remember correctly. I got as far as El Volcan before the carbineros turned us around, saying it was getting too late and transport options would dwindle rapidly as the sun waned. I think they were right.....
I have heard that access to the volcano from the Chile side has unfortunately gotten very difficult in recent years due to the hydo plant.
Most people climbing Volcan Maipo are now doing so from the Argentina side. This photo is from that side.
Well that explains it. Next time I am fortunate enough to get down there I won't be left wondering. Thanks for the update