The vast project -- costing more than London's 2012 Olympic stadium or France's 2.5 km (1.5 mile) Millau viaduct which is the world's tallest bridge -- should transform the decades-old transport hub and underground mall into a striking visual landmark, even if Parisians are divided over the aesthetics.
The city's latest grand architectural project follows the building of a giant glass pyramid as a new entrance to the Louvre museum and a book-shaped national library by the Seine.
The architects plan to put together the 17,000 sq meter canopy offsite and erect it in one piece.
"We'll bring it in almost pre-fabricated, and everything has been designed to rest on the existing underground structure without adding any more pillars so as not to disrupt activities," Patrick Berger, one of the designers, told Reuters.
The renovation, set for completion in 2016, will include a redesign of the site's 10-acre garden and a revamp of the underground station. One of Europe's busiest, it connects five metro lines and three suburban train lines including the one that brings in visitors from Roissy airport.
But it is the undulating canopy with its pillarless greenish-yellow louvered roof that will take up the bulk of the cost and which is attracting the most criticism.
"It's going to be an absolute catastrophe. Architecturally it's rubbish and financially it's a scandal. The cost is absolutely astronomical," said Elisabeth Bourguinat of local association Accomplir which is fighting to halt the plans.
The louvered glass slats could let in rain, critics say, while the steel cables needed to stop the roof from caving in may block natural light, making electric lighting indispensable.
Planners defend the design and say it will open up the confined and in places tatty underground shopping center, creating a much-needed sense of space and accessibility.
They also say the cost is worth it for such a long-neglected and emblematic site. Formerly a bustling wholesale food market, immortalized by Emile Zola as the "belly of Paris," Les Halles is a gateway today into the center of Paris for millions of commuters, tourists and youths from the city suburbs.
"We see it as a work of architecture, something that is completely in tune with the times, something that will leave a beautiful and lasting mark on the heart of the city," said Anne Hidalgo, deputy mayor of Paris.
Few would deny that Les Halles is badly in need of a makeover, to rid it of the stigma of a 1970s urban regeneration project widely regarded as a failure.
The original food market was moved out of the city to the now famously sprawling site of Rungis, and the elegant 19th century steel and glass pavilions designed by Victor Baltard to house the stalls were all ripped down.