The final project on our list of the 25 most significant buildings of the 21st century is the restoration of the Grand Palais in Paris by Chatillon Architectes, bookending our series with two powerful stories of reuse and renewal.Few buildings garnered as much international attention in 2024 as the Grand Palais, even though it was built 124 years earlier.The sweeping glass and steel structure on the Champs-lyses reopened following its first major restoration, securing its place as a venue for the Paris 2024 Olympic and Paralympic Games.It was a herculean effort led by the French studio Chatillon Architectes, which guided a team of 1,000 artisans from over 50 companies to turn the project around in under four years.Though the Grand Palais was already one of Paris's most loved landmarks, these efforts gave rise to what became a centrepiece of the event. Echoing the ethos of the 2024 games touted as the greenest ever it illustrated the value of preserving architectural heritage.It is a fitting end to our series, which began with the Tate Modern an art gallery in the shell of an abandoned power station completed in 2000 by Herzog & de Meuron.Together, the projects offer a masterclass on how a building's history can be respected while being brought up to modern-day standards with contemporary tools, sending a pertinent message to the architectural community as it navigates an age of demolition.The Grand Palais was the most significant building of 2024The Grand Palais is arguably best known for its vast and intricate barrel-vaulted atrium, or nave, which is crafted from more than 6,000 tonnes of steel. It is crowned by the largest glass roof in Europe.Upon its reopening, architecture critic Stephen Zacks described the renovated building as "a show-stopping 21st-century centrepiece".Meanwhile, the Financial Times hailed it as "an architectural cadavre exquis", where "everywhere you look there are treasures".A show-stopping 21st-century centrepieceStephen Zacks in MetropolisThough the 72,000-square-metre landmark stole the limelight in 2024, the building's significance runs to long before that.Built to host the Paris Universal Exhibition in 1900 to showcase French art, it has served as an ornate backdrop to many international exhibitions and events, ranging from Chanel fashion shows to art fairs including Art Basel Paris.More somberly, it was even used as a world war one military hospital and, during the Nazi occupation of Paris, as an exhibition space for propaganda.Originally built in 1900, it reopened last year following an extensive renovation by Chatillon ArchitectesChatillon Architectes' ambition for the project was to preserve and celebrate as much of the original Beaux-Arts structure as possible, honouring the original vision of its architects Henri Deglane, Albert Louvet, Albert Thomas and Charles Girault.Changes have included reopening areas once closed to the public, and the carving out of a sightseeing route into its plan. Its building services have also been modernised, bringing the building up to the standards of a modern-day events venue.The scale of work was so unprecedented it required the studio to split it into two phases, with the first centred around the nave, ensuring it was ready to host fencing and taekwondo events in the Olympics.We have approached the project with a contemporary mindset, ensuring that the building is prepared for its next phase of lifeFrancois ChatillonThis phase also involved improving the link between the Grand Palais and the surrounding gardens, while reinstating the building's original central axis across its Hshaped plan, reconnecting its three main spaces including the nave.In the nave itself, Chatillon Architectes restored the ornate balconies and improved escape routes, allowing its capacity to increase by more than 60 per cent.The second phase, which is yet to complete, is focused on its surrounding rooms. Its full reopening as a sporting and cultural events venue is expected in 2025, when the Centre Pompidou will temporarily move into the galleries.The building was used as a venue for the Paris 2024 Olympic and Paralympic Games"The scale of the project is quite unbelievable, from the design stage to the construction," studio founder Francois Chatillon told Dezeen on a tour of the building before its opening."We have explored thousands of archival documents to truly understand the building and its original intentions," he continued."Our focus has always been to honour and restore the best of the building's past but not to do this blindly. We have approached the project with a contemporary mindset, ensuring that the building is prepared for its next phase of life and that, above all, it is a functioning building for modern society."When French president Emmanuel Macron announced plans for the project it was met with scepticism due to the quick timeframe in which it was to be delivered. Next to the restoration of the fire-damaged Notre-Dame Cathedral, it is reportedly the country's largest public building project.Read: Herzog & de Meuron's Tate Modern was the most significant building of 2000"Four years ago, we were told that it was still crazy," said Macron of the Grand Palais restoration. "But now the whole world will rediscover the Grand Palais as a place of creation, of exhibition, of knowledge, of welcoming the public."Giving the building back to the public in this way was always the overarching goal of the studio, according to Chatillon."Our main objective from the very beginning was to make the Grand Palais a public building again," he said. "In recent times, it is a building that has been accessible on occasion but not possible to truly experience it became a monument that was often only observed from afar.""We have been able to make the Grand Palais a functioning building once again and one that the public can now truly enjoy and explore."Did we get it right? Was the Grand Palais renovation by Chatillon Architectes the most significant building completed in 2024? Let us know in the comments. With all 25 buildings revealed, we will be running a poll to determine the most significant building of the 21st century so far.This article is part of Dezeen's21st-Century Architecture: 25 Years 25 Buildingsseries, which looks at the most significant architecture of the 21st century so far. For the series, we have selected the most influential building from each of the first 25 years of the century.The illustration is byJack Bedford and the photography is by Edmund Sumner, unless otherwise stated.21st Century Architecture: 25 Years 25 Buildings2000:Tate Modern by Herzog & de Meuron2001:Gando Primary School by Dibdo Francis Kr2002:Bergisel Ski Jump by Zaha Hadid2003:Walt Disney Concert Hall by Frank Gehry2004:Quinta Monroy by Elemental2005:Moriyama House by Ryue Nishizawa2006:Madrid-Barajas airport by RSHP and Estudio Lamela2007:Oslo Opera House by Snhetta2008:Museum of Islamic Art by I M Pei2009:Murray Grove by Waugh Thistleton Architects2010:Burj Khalifa by SOM2011:National September 11 Memorial byHandel Architects2012:CCTV Headquarters by OMA2013:Cardboard Cathedral by ShigeruBan2014:Bosco Verticale by Stefano Boeri2015:UTEC Lima campus by Grafton Architects2016:Transformation of 530 Dwellings by Lacaton & Vassal, Frdric Druot and Christophe Hutin2017:Apple Park by Foster + Partners2018:Amager Bakke by BIG2019:Goldsmith Street by Mikhail Riches with Cathy Hawley2020:Anandaloy by Anna Heringer2021:Sara Kulturhus by White Arkitekter2022:Reggio School by Andrs Jaque2023: Third Space by Studio Saar2024: Grand Palais renovation by Chatillon ArchitectesThe post The Grand Palais was the most significant building of 2024 appeared first on Dezeen.