Every time I come to Buenos Aires I make sure that I go visit the Sunday antiques fair in San Telmo. It has expanded a lot since my first visit in 2006, and my last in 2010. Calle Defensa is now closed to cars and it’s lined up with stalls selling all sorts of stuff from antiques, clothes, souvenirs, etc. There are also a lot of a stalls selling very good street food.
I got there kind of late and only had one and a half hours to explore. Not nearly enough. It was very very crowded. I might make another visit this Sunday and try to get there early when they open at 10am.