A sprawling concrete-and-glass monstrosity, the neon-lit underground shopping centre stands, outmoded and crumbling, on the site occupied for centuries by the central Paris food markets, France's equivalent of Covent Garden.
Its construction in the 1970s led to long-running protests as the area known as the belly of Paris became a building site for nearly a decade. It is now run down, vandalised and thoroughly unappealing, and the municipality wants to turn it into a spectacular attraction as popular with visitors as the Eiffel tower, the Pompidou Centre or the Louvre Pyramids.
"I'm aware that we are venturing into very sensitive territory," said the mayor of Paris, Bertrand Delanoë, who must choose between four projects by the end of next month.
"I have no intention of imposing another trauma on this long-suffering neighbourhood. But this site is too symbolic of the centre of Paris for us to make another mistake of it."
Le Forum, which draws tens of millions of visitors a year, stands on a 15-hectare site bounded by the rues de Rivoli, Etienne Marcel and Louvre, and by the Boulevard Sebastopol. It currently houses an RER suburban railway station which handles 800,000 passengers a day, some 180 shops on four different levels, playgrounds, a swimming pool, cinemas and exhibition spaces.
But the decaying, graffiti-covered concrete walls of the cavernous mall, its strip lighting, sad stores, leaking roofs and unsavoury gardens - long a rendezvous for drug dealers - have become an embarrassment in a city that prides itself on combining architectural classicism and innovation.
Chic Parisians, wary of the mall's dodgy reputation as a daytime hangout for disaffected suburban youth, would rather shop elsewhere.
"The Forum is an ageing eyesore and it does not represent the vision of the centre of Paris that either the city council or most local residents would like to give," said a municipal spokesman. "We need to do something radical; something that everyone can be proud of."
Four projects have been submitted. The first, by the French architect David Mangin, envisages large, completely remodelled gardens and a wide promenade "like Barcelona's Ramblas", ending in a glass roof suspended nine metres above the forum.
It has won the support of most locals, who say they appreciate its green spaces, play areas for children, capacity to house food stores, and low height. "Of all of them, this is the only one that seems really to have taken into account the wishes of the local people," said Gilles Pourbaix, the head of one neighbourhood association.
The most spectacular project is that of Jean Nouvel; it is composed of vast green spaces at three different levels, including a hanging garden 27 metres (90ft) high, offering a breathtaking view over the city.
"Lots of people are drawn by that one," said Mr Pourbaix. "It's innovative all right, but we say simply that it would deprive the entire neighbourhood of all daylight."
The other plans, by the Dutch architects Winy Maas and Rem Koolhaas, propose respectively a huge glass roof covering some 40% of the Les Halles site; and 21 coloured glass pyramids dotted over the whole area, each offering access to a radically remodelled interior.
Mr Delanoe said he had no favourite, but added that "none of these projects is acceptable exactly as it stands".
Work is scheduled to start in 2007 and should be finished, demonstrations of local feeling permitting, in time for the Olympic Games that Paris hopes to host in 2012.