Shadowy lanes draped with awnings lead through foodie mayhem. Dense with smoke from sizzling comales and hotplates and steam from bubbling cazuelas of goat stew, the laby rinth is a Mexican arcadia. You might trip over a live turkey or two, a rabbit, cockerel or chicken before entering the alley of flowers: kaleidoscopic, fragrant and exuberant. This intensely sensory world is dominated by Zapotecs and Mixtecs, two of 16 ethnic groups in the Oaxaca region of southern Mexico, the women dressed in dazzling embroidered tunics crowned by satin ribbons plaited in their hair - a style brought to the outside world by Frida Kahlo - while the men stick to cowboy hats.
But this is no art gallery, it is Oaxaca's Central de Abastos ("supplies centre"), said to be Latin America's largest indigenous market, a functional feast for the senses that feels completely timeless. Food is everywhere, in every form, side by side with potters, ironmongers and tiny, fly-blown bars where a glass of mezcal is served with a saucer of chapulines (fried grasshoppers). Meanwhile, over in the centre of this beautiful town, the intense native soul morphs into a mestizo world of hip boutiques and restaurants, including one of Mexico's finest sources of nueva cocina, Casa Oaxaca.
D H Lawrence wrote about the market back in the 1920s and it has barely changed since. His description of the sounds, "as if all the ghosts in the world were talking to one another . . . a noise something like rain, or banana leaves in a wind", still holds true, though younger "ghosts" may wear jeans, T-shirts and baseball caps. Rain there is little of in the surrounding cactus-studded hills, but somehow the valley churns out a cornucopia of produce, including dozens of different corns, chillies, plump tomatoes, tomatillos in papery skins, knobbly avocados, pumpkins, black beans, fat, sunny mangoes (the sweetest in the world), limes and plums, one of which, the zapote, gave the hedonistic Zapotecs their name.
In one alleyway a line-up of village women stands patiently, each woman clutching a sack of home-made tlayudas - gigantic, fresh tortillas, ready to sizzle. Regulars make a beeline for their favourite; there is no price comparison at this level. Then there are the butchers who string up curtains of thinly hammered beef, arrange a pig's head or a row of chickens with their spiky yellow feet, something we forget about in our shrink-wrapped world. And between the piles of fruit, sacks of different chillies and mountains of egg-trays, you might spot a little altar with flowers and flickering candles in front of a saint's image.
Catholicism officially replaced indigenous beliefs with the Conquista 500 years ago, yet some aspects linger on. Abigail Mendoza, a joyful, buxom Zapotec cook who lives in the weaving village of Teotitlán, tells me how eating is still considered sacred by her people. Fiestas are the big moment, entailing days of food preparation, and recipes are so localised that each village has its own. As the eldest of ten siblings, Abigail started grinding corn and making tortillas at the age of six ("My mother was busy having babies").
Looking at her tiny, plump hands, I wonder how many chickens and turkeys they have jointed, how many unctuous moles they have stirred over the years. Every utensil is vital, too, from the clay pot used for a dessert, which imparts a particular flavour, to the metate, a lava-stone grinding surface, on which she rolls, breaks down and gradually liquidises her blocks of cooking chocolate. This produces one of Abigail's tours de force, xocolate con atole, pretty much the same chocolate drink adored by the Aztec emperor Moctezuma, frothy as a daydream, contrasting cool with tepid temperatures and spiked with cinnamon, almonds and maybe a hit of chilli. Pure, exotic delight.
On a typically bright Sunday morning in Zimatlán, another village of this tentacular valley, I go to watch Alejandro Ruiz Olmedo play football with a team of carpenters and bus drivers. This is not due to some atavistic yearning on my part - far from it - but rather because I am curious to see this highly successful chef outside his elegant restaurant, Casa Oaxaca, and back on his home turf. As the oldest in the team (he's 37), Alejandro sticks to being goalie, but his leadership skills are obvious. Born and bred in this village as the eldest of five children whose mother died when he was 12, Alejandro entered the kitchen early on. Since then he has climbed the rungs not only of Mexican gastronomy, but also of society. Today he travels the world and greets glitterati at his restaurant, yet he will still man the pots and pans or develop an ambrosial new dish.
With an effortless ability to communicate, Alejandro embodies the good-humoured, open spirit of the valley, as well as its incredible industriousness. Yet he is only too aware of the downside, lamenting the high unemployment and explaining how emigration is breaking up families (many of the illegal "wetbacks" climbing the wall into the US are from Oaxaca). The solution? For Alejandro, it can only lie in the world of food and drink, above all in the development of the valley's traditional mezcal industry.
Apart from Malcolm Lowry's ambivalent hom age to mezcal in Under the Volcano, the notoriety of this alcohol made from the agave plant stems mainly from the worm lurking in the bottle. Yet production is still limited, trailing far behind its cousin tequila, produced in a certified region near Guadalajara, in central Mexico. Still a cottage industry, mezcal is made in small, family-owned distilleries around the Mixtec town of Mitla. There is growing interest in its smooth, honeyed flavour, however, and mezcal bars are spreading in Mexico City. Another of Oaxaca's more innovative restaurants, Los Danzantes, has actually pioneered setting up its own distillery and distributing its label. Alejandro is on a similar track, so maybe, one day soon, those market souls, those ghostly voices, will emerge from the shadows into a more remunerative world.
Fiona Dunlop is the author of "¡Viva la Revolución! New Food From Mexico", published by Mitchell Beazley (£20)