I lived in Salta for a few months, so I got the chance to explore the region like it should be explored! And what a sight to see... Incidentally, if you ever have any doubt concerning your trip, you should really consider including this part of the country on your trip into Argentine lands, as much for its culture as for the insane landscapes found there.
Among the many things to explore in the area, the Quebrada del Toro is a rather nice option, especially if you go towards the "salar" (or salt flat). I took a crazy long time to decide to take a tour there, especially because the idea of going up in the Train to the Clouds never really excited me. So I finally went there by car, and I have to admit the landscape blew me away once again: new mineral scenery based on unusual shapes and colourful strata; it's impossible to get bored! Attention, get ready to take out your camera in burst mode, as you'll certainly want to capture every moment spent there.