Christian's place is smack dap in the center of the Central Historico district. Super close walking to the Zocolo and tons of great restaurants and taco stands - I recommend Los Coyucos, which is only a few hundred feet away and has been featured by many food bloggers as well as Anthony Bourdain. The only downside is that because of the location it can be pretty loud for most of the night so if you're looking for a nice relaxing area this may not be for you.