From my hotel room the town of Chihuahua looked like the most haphazard of urban sprawls, its ancient buildings swamped by new concrete. Out on the streets it was a different story.

On the plaza de Armas, in front of the cathedral, there was a central bandstand with four elegant gazebos keeping it company - this was the territory of the shoeshine boys, some of them old enough to have come over with Cortes. They taunted me as I walked by, laughing and shouting.

"Hey, gringo, you want me to shine your shoes?"

Perched on elevated thrones sat their customers, manly men in white stetsons, godlike, reading newspapers while their feet were caressed. A stately eccentric preceded me across the square. She wore a sombrero, and a flowing violet cape streamed from her shoulders. Under the several layers of her frock were pink socks and short cowboy boots. She was smoking like nicotine was air, the cigarette planted in the middle of her moist and scarlet mouth, blowing the smoke from her nostrils in straight, forceful bursts. She was majestic and large and sailed forward like a battleship; solid and strong, capable of a dangerous broadside.

In the calle Libertad there were no motor cars, only people, lots of them.

It was a smiley place without a sign of the pickpockets and bag-slashers the guidebooks had warned me were prevalent in Mexico. Everything was on sale in this street: floating balloons, jumping furry animals, gaudy jewellery, besoms and buckets, liquorice and marshmallow in enormous transparent sacks, gobstoppers and lollipops galore. The clothes shops were submerged in pop music and girls bulging out of their jeans. The street food stalls had barely a yard between them; ice creams, tacos, churros , elotes , dulces and banderillas .

A pile of sombreros glided by, borne on a man's arm. He must have been carrying 40 or 50 in a stack; the cheap ones stamped out in plastic, the expensive ones woven in bleached straw. Their form was classic - high-crowned with perfect aerodynamic brims swept back to curl, arrogant and debonair, above the ears.

On the benches, and cross-legged on the ground, were the Indian women, wearing dazzling shawls and blankets, headscarves and skirts; small children tied to their backs. One of the women leant her weary face against the wall; her daughter of eight or nine was selling home-made paper flowers from a cardboard box. Her garments glittered; a silver top, a rainbow dress, a red-check apron, a turquoise sweater tied around her waist, and into her crow's-wing hair she'd thrust one of her own blossoms, magenta and fluorescent.

And outside a draper's, a six-piece band entertained the whole world, stetsons low on the brow: banjo, guitar, saxophone, accordion, violin and trumpet. The music was spirited - a "south-of-the-border" western rhythm, inviting dance, certainly in the case of the battleship I had seen earlier on cathedral square. She bore down on the musicians like a dreadnought and, with no change of expression, she began to circle them in a kind of regular-paced, prancing hop, occasionally pirouetting, her eyes fixed, her mind lost in its own revels.

"It's the best place to make a start in Mexico, Chihuahua," someone had told me on the plane, and they were probably right, but Chihuahua, much as I fell in love with it, was not the reason for my trip - the Chihuahua-Pacifico Railway was: the Copper Canyon Line, one of the most extraordinary stretches of railway in the world, and one of the most spectacular.

Only completed in 1961, its 650km took 90 years to build. It twists and turns through mountain valleys; it clings to the sides of volcanic cliffs, plunging through 86 tunnels and rattling over 39 bridges on its way through the Sierra Tarahumara, a sierra that is named for the 50,000 Tarahumara Indians who live there, the least assimilated Indians of North America.

I was at the station at 6.30 the next morning, destination Los Mochis, only 20km from the coast of the Pacific Ocean. It was dark and very cold. I couldn't see much of anything around me, but there was old rolling stock mouldering in the sidings, and maybe a score of people already boarding the train. In the hall that doubled up as ticket office and waiting room, half a dozen Indian families, as enduring as rock, squatted under blankets, waiting for the second-class express that wouldn't be leaving for another 24 hours.

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