Try any of the finest local beers, although is not really local, it's part of a global company. Tango time!
I went here during the weekly Sunday street fair and it was a feast for the senses. If you are in San Telmo, this is a must go place. There were vendors, artist and street performers. This is the best place to buy souvenirs as there are a lot of options and the prices are relatively cheaper. Be very careful of pick pockets.
at sunday's very good!
Come for the tango. Come for the art and antiques. Come for the bohemian district that is San Telmo. Heck, just come to Bar Dorrego and have a submarino (if you don't know what this is, I'm going to tell you to trust me and order it if you like hot chocolate). And when you're done exploring San Telmo, try dinner at El Baqueano nearby (waaay advanced reservations required) or make your way over to Puerto Madero.