Salta's a favorite, but we didn't get much time for exploring. Bill and Inga had only one day, then flew out to Iguazu Falls the next, so we spent it going up the tram to the top of Cerro Bernardo. 

The city has made a beautiful park on the mountain top with an amazing series of waterfalls--Becky, you can get some more ideas, maybe? I can see Jeff now making plans for the tram.