Barrio Antiguo provides you a glimpse into the Monterrey of yesteryear. The houses and cobblestone streets are charming and full of little shops, antiques, restaurants, cafes. On sundays, they close one of the streets (Mina?) and local artisans and antique dealers set up tables to sell their wares. They open at around 1pm, until early evening (7pm?). There are lots of really nice restaurants in the area. Parking is a problem, but if you don't mind parking on the outskirts and walking in, it's totally worth it. It's approximately 3 blocks from the "zona hotelera" where all the bigger hotels are, and where there is a metro station too. Barrio Antiguo makes for an excellent day trip, or even half a day. Oh, and it's close to the MARCO, modern art museum, so you could do that in one day easily.