Oaxaca's tourist footprint is remarkably small. The Zócalo, the pedestrianised Andador Turístico running north from it, Santo Domingo at the top, and the dozen or so blocks in between — that is very nearly all that most visitors see in a week. Step three or four streets past that boundary in any direction and the prices fall, the crowds vanish, and the city resolves into what it actually is: a collection of distinct old barrios, each organised around its own church and its own small plaza, several of them older than the colonial grid that grew up around them.
This is less a secret than a habit. The centre is compact, handsome and relentless, and it is built to hold you. The barrios ask for a twenty-minute walk and hand back a version of Oaxaca where the person next to you at the comedor counter is having lunch rather than an experience.
How long to give it, and in what order
Do not attempt these in a single day. Six barrios in eight hours produces six interchangeable memories of a church and a plaza, and misses the entire point, which is that each of these places is worth seeing at one particular hour and is fairly dull at all the others.
The honest minimum is two half-days folded into a longer stay — one morning and one early evening — and the better approach is to treat the barrios as what you do between the set pieces rather than as a day of their own. If you have four days in Oaxaca and Monte Albán, Hierve el Agua and a mezcal-valley trip are already on the list, put Jalatlaco on your first evening: it is five minutes from most central hotels and it will immediately recalibrate what you think this city looks like. Give Xochimilco a morning when you would otherwise be queueing at Santo Domingo. Save La Noria for the evening you cannot face another restaurant with an English menu.
The rhythm that works is simple. Markets before about eleven in the morning, when the produce is fresh and the comedores are cooking for people on their way to work. Plazas from roughly six in the evening, when the heat lifts and the barrio comes outdoors. The hours in between are the worst possible time to be in any of them — shutters down, nobody about, and flat midday light on the painted walls that were the whole reason you walked out there.
Sunday is the quietest day in the city and frequently the most local, with families in the plazas and very little commerce anywhere. It is also the day a good number of cafés and bakeries close, and Monday closes a further tranche of restaurants, so decide where you are eating before you set out rather than after.