The Louvre's northern exposure

At first sight, the Louvre in Lens could hardly be more different from the original: one is in a grandiose royal palace in the heart of Paris, the other is in one of France's poorest towns, battered by the First World War and synonymous with industrial decline after the end of coal mining.

What the Louvre president Henri Loyrette is calling "the other Louvre" is a bold bid - a "national" museum going out to the nation in a move intended to boost the area just as the Guggenheim did for Bilbao. And, as with the future Louvre Abu Dhabi, the Lens offshoot attempts to present a snapshot of the original Louvre to a public that is not always used to museum-going.

"Two things would spell failure in my eyes," Loyrette says. "The first would be if the population doesn't take ownership of the museum. The second would be if the Louvre's existing visitors don't go."

Lens is just one hour by train from Paris and the Louvre Lens's director Xavier Dectot hopes to attract 700,000 visitors in its first year and half a million every year after that - compared with the nine million annual visitors to the Louvre itself.

The building, designed by the Japanese architects Sanaa on a former pithead in what will soon be a spacious public park, seeks to make the most of natural light. The low, one-storey structure, with a glass entrance pavilion and long, burnished aluminium boxes spreading out either side, is surprisingly discreet from the outside, virtually disappearing into the grey sky on the December day when I visited. Quite a contrast to the excitement of the interior. "We wanted a space where people can meet the Louvre's works in a new way," says Kazuyo Sejima of Sanaa.

The new way is the Grande Galerie, the equivalent of the permanent collection, on display for five years (a few works will be changed each year) in a single open space, with no room divisions and no works along the sides. Instead paintings are on small upright panels and sculptures on plinths or grouped in islands, with light filtering in from above and polished aluminium walls that create soft reflections.

For the opening display, the Galerie du Temps(Gallery of Time), 200 works take you through six millennia of history, arranged chronologically. It doesn't sound radical, but it is a daring break from the convention of arranging museums by departments - an idea that has existed at the Louvre for 200 years.

It offers an opportunity for meetings between civilisations and techniques - mixing sculpture, paintings, ceramics and metalwork - and a reminder of the constant dialogue that existed in the past between different cultures, neatly symbolised by the 16th-century Venetian painting The Reception of the Venetian Ambassadors in Damascus. Unlike in the Louvre Paris, in Lens you can see Greece alongside Egypt and the Near East, Gothic at the same time as Islamic. It opens with an inspirational ancient world span - an early female idol from the Greek Cyclades, a quirky terracotta-eye idol from Syria, circa 3300-3000 BC, or the determined-looking figure of Gudea, the prince of Lagash, in black diorite from Mesopotamia, circa 2120 BC.

"It was an extraordinary pleasure to be able to rethink the museum like this. Normally, we are highly specialised. Here it is decompartmentalised in every sense," says Vincent Pomarède, the joint curator of the Galerie du Temps. And you get the feeling that the curators had great fun picking from the Louvre's treasure chest for a display that is full of parallels and contrasts, not only in style, materials and scale, but also in gestures and expression: the Renaissance marble torso of Mercury next to Perugino's extraordinary Saint Sebastian, piously oblivious to the arrows that are making him a martyr, or the shared pose of an oil portrait by Rigaud and a terracotta bust by Coysevox.

Loyrette has described "the other Louvre" as a laboratory and this refreshing display is a stimulating vision of what a museum can be. The Louvre has sent out some of its most famous masterpieces, but there is also the space here to discover lesser-known works.

While many museums impose a route - directing your thought and movement - here you are encouraged to meander. You can follow the chronology, read by region or zigzag by themes - male and female nudes, secular and spiritual, or the portraits of rulers and representations of power that punctuate the entire chronology.

Galerie du Temps closes at about 1830, with Ingres's portrait of Louis-François Bertin, representing the power of the press; a portrait, attributed to the 19th-century Iranian artist Mehr Ali Shah, of a jewel-encrusted Fath Ali Shah; and Delacroix's Liberty Leading the People, which has virtually become the symbol of the museum, as the Louvre exchanges its palace in Paris for a palace for the people.