There is this shopping mall in Buenos Aires that I frequented several times while I was there: the Galerías Pacífico. This Beaux Arts building was constructed in 1889, and still stands today housing several luxury shops. And the interior is nice.
I checked this place out several times, mostly for the architecture. But there's actually more than that. There was a tango class in one of the halls, and so I hung out there for a while to watch people dancing. There's also a large art gallery complex at the very top, where I saw quite interesting pieces. Overall, it's an interesting place to briefly discover.
Later on, when I was in Buenos Aires again (I was in the city twice during the course of this trip), I visited this place again with my sister and brother-in-law. We checked out the art galleries, and even bumped into some of the artists whose works were on display.
As I said, it's an interesting place to check out. If you need food, there's restaurants and cafes. If you need a luxury item, there's shops for it. And of course, if you just want to kill some time, then there's also plenty of opportunities for that.