The San Telmo district is a must-visit as it preserves the old Spanish style architecture and streets. The roads tend to be paved with cobblestones, lending a quaint and romantic feel to the area. You seem to be within a little slice of historic Europe. It is however, a very touristy area and don’t be surprised of you are offered ‘authentic’ Argentinian items for sale at sky high prices. There are markets held on the Plaza Dorrego every Sunday, be sure to catch them if you’re in the area, they have a great community feel.