It s like a great big medieval loudspeaker broadcasting God the woman next to me whispered. And even a half-baked atheist like me could have no doubt that God – whether you believe in him or not – is sitting right at the centre of the ancient city of

It's like a great big medieval loudspeaker broadcasting God" the woman next to me whispered. And even a half-baked atheist like me could have no doubt that God - whether you believe in him or not - is sitting right at the centre of the ancient city of Chartres.

The famous French cathedral can be found in a small square right at the top of the hill, surrounded by a jumble of old houses, cafes, shops and bars, Any spare spaces around the base are filled with bright flower-beds, demonstrating the local council's determination to live up to their boast of being one of the region's top villes fleuries. Two enormous un-matching spires point at the sky and the stone facade seems almost alive, for it is covered with hundreds of carvings.

To the many pilgrims who have flocked here throughout the centuries, this huge building with its elaborate decoration must have seemed like a great story book of faith. Each feature has a meaning, each carving a significance. The biggest set-piece is above the main entrance, showing the Apocalypse of Christ in Glory, surrounded by beasts representing the four Evangelists, the twelve Apostles and a host of angels.

Step inside and you are plunged into a breathless darkness, with immensely high, thin windows sparkling gently all around you like jewelled kaleidoscopes. Nearly all of the famous glass in Chartres dates from the thirteenth century. Amazingly, in the lowest panels of some of the windows, are images of the people who actually paid the cost of making them.

Here they are, as brightly coloured as they were eight hundred years ago, toiling away at menial tasks. Water carriers, stripped to the waist, hauling heavy buckets up the cripplingly steep hill; cobblers, mending the worn-out shoes of people who could not afford to buy new. These people lived harder lives than we can imagine, yet their achievement, in creating this soaring building with their hand-tools and ox-carts, illuminates the power of their faith.

The cathedral's great stone labyrinth continues the theme of offering hardship to achieve grace. It is set flush into the floor of the nave, and every Friday the chairs are moved away to reveal it fully. It is intended to be followed upon the knees, embracing physical discomfort or even pain, to make the difficult progress towards the holy centre.

Chartres has always attracted pilgrims who come to venerate its holy relic of the Virgin Mary and admire its marvels. But in our secular age, those who care for the cathedral must work hard to keep the visitors coming, and spending, since there is no entry charge. The latest idea is to allow small groups to tour the crypt by candlelight. You either come with your own group, or apply to join an existing group.

You meet after dark, and are issued with tall wax tapers, whose flames are the only illumination as you descend into pitch-darkness. It is then a magical experience to progress slowly beneath the low ceilings, gazing at the medieval wall paintings by the light of the flickering candles.

Several tall Gothic statues, which survived a twelfth century conflagration have also been preserved down here. Over three metres tall, and far thinner than any normal person, these weirdly elongated statues have beautiful, naturalistic heads, which bestows a compelling presence, as though your candle is revealing a creature from another world. The sculptor Rodin is known to have been enthralled by them. After studying them for a long time, he eventually wrote to his family that, although he could produce something that looked like them, he could never produce anything that actually was like them.

At the far end of the crypt are stairs that lead up into the darkened, silent cathedral itself. Small racks of votive candles in red glass holders flicker against the vast black space in bright pools of white and scarlet, reflecting dimly off polished stone. You can barely see the walls and roof some distance away, for the great glass windows permit only the faintest moonlight. You can only tell the size of the place by the echoes coming back at you from the shadows.

All this intensity can seem overwhelming, but on summer evenings, a son-et-lumiere show outside in the square lightens the atmosphere. Shortly after dark, music starts booming from cunningly positioned loudspeakers, and the cathedral's facade becomes a great screen for moving images representing its history: the kings and queens, the tumbling stones of war, the fires and the dove of peace.

It is a tiny bit like the sort of show they have at Walt Disney World in Florida. Yet the solemn statues still gaze out with the dignity of hundreds of years beneath the moving colours. Times change, they seem to say Yes, today it is son-et-lumiere. But next century and the century after that - who knows?

Book for the cathedral tour via Chartres Tourist Office, Place de la Cath�drale, 28005 Chartres ( +33 (0)2 37 18 26 26,

Email: info@otchartres.fr,

Website: www.chartres-tourisme.com

Jenny travelled to Chartres via Rail Europe http://www.raileurope.co.uk/

More information on the region from Loire Valley tourist board http://www.loirevalleytourism.com/