After having travelled Argentina, La Quiaca plunged us into a very different, Andean culture.. Here, everything makes you think you are already in Bolivia, especially as the frontier is just a few steps away!
The restaurants have cheap local dishes, so why not stop and have a bite to eat before walking the last few hundred metres to go over the Bolivian border. What's more, the locals are very welcoming. From Villazon, on the Bolivian side, you can get a train, bus or mini-bus to go to Tupiza.
As far as I was concerned, there wasn't anything to keep me there for more than an hour as I had already travelled round the north of Argentina before. But this village seems to be a departure point for visiting the surrounding region before going on to the neighbouring country.
In Jujuy province the influence of Andean culture is definitely more tangible than in the rest of Argentina, which means that La Quiaca is a great place to cross into Bolivia from! In any case, if you are thinking about going over the frontier during your trip to Argentina, this is definitely the best place to do it. The two other crossings don't have as many buses, taxis and trains going to them!
Other than that, the only thing to say about La Quiaca is that its a typical border town. So there's not a lot to do in the place except get your passport stamped so you can go to another country.
I only stopped briefly there, just long enough for the customs officers to look around the bus and at all the passengers bags. Some people told me that they had a dreadful time there because the customs officers are determined to do a really thorough job and find anything at all that gives them a reason to function (and there is quite a lot of smuggling and other dubious trading going on here). That may be, but when I went it was fine.