In 2000 the legendary gallery owner and art dealer Yvon Lambert offered hundreds of major works by the cream of contemporary artists to the city of Avignon for the Collection Lambert.
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Lambert had strong and specific tastes. He was drawn to minimalism and conceptualism and to American (though not exclusively American) art. Although he was based himself in Paris, he did not view that city as the centre of the international post-war art scene.
Anselm Kiefer, Douglas Gordon, Nan Goldin, Cy Twombley, Julian Schnabel, Jean-Michel Basquiat and Andres Serranno are among his collection. Many of their pieces were acquired at early stages in their careers.
The Collection Lambert is one of the biggest holdings of modern art of this calibre in France, and one of the boldest. It was originally in Avignon on long-term loan. In 2012 it became a permanent donanation.
However there were strings attached to Lambert's gift. The Collection Lambert had been confined to Avignon's Hôtel de Caumont, an elegant 18th century hôtel particulier (private town house).
As many of the works are very large, they had to be kept in store most of the time for lack of space. Instead the Collection was mainly renowned for its superb and ambitious temporary exhibitions.
Pictured: the sweeping cobbled courtyard of the Hôtel de Caumont, looking very much like a delightfully experimental children's adventure playground when we first visited the gallery in 2011.
So Lambert's donation was dependent on the museum's expanding into the next-door building, the Hôtel de Montfaucon, formerly an art school.
The work took two years and cost 15 million €uros. But it is now complete. We went along to take a look and it's mightily impressive.
The museum's exhibition space has doubled to around 6,000 square metres / 64,600 square feet. And much more from the Collection's permanent holdings are now on public display.
Temporary exhibitions are on show in the Hôtel de Caumont and the permanent collection is in the Hôtel de Montfaucon.
The two buildings are connected by what the architects describe as a little "chapel" - in fact it's a luminous white stairwell centred around a dramatic and beautiful swirling spiral staircase.
The conversion has been designed to retain maximum flexibility, and a sense of contrasting atmospheres are you pass from space to space. The layout of the complex as a whole is maze-like and you feel yourself immersed and almost lost in the art.
Each room seems to be a different shape and to have a different atmosphere. Painted plain white, they feel very modern and minimalist, despite the building's perfectly preserved period exterior. Pictured: Works by Jean-Michel Basquiat at the Collection Lambert.
The new complex also includes a "project room" for special events, a large bookshop, an excellent restaurant, Le Violette, an apartment for artists in residence and an area for educational activities.
There's a cinema auditorium too, decorated entirely in Yves Klein bright blue, from the curtains and walls to the steps!
Recent shows at the Collection Lambert have featured the American artist Cy Twombly, Lawrence Weiner, the Brazilian photographer Vik Muniz and the trail-blazing French theatre, opera and film director Patrice Chéreau, who died in 2013 and who had a close association with the city and with the Avignon Theatre Festival.
The Collection Lambert is also temporarily hosting a sculpture capturing France football captain Zinedine Zidane's notorious headbutt of a fellow footballer during the 2006 World Cup final.
Coup de tête (Headbutt), pictured, shows Zidane charging at the Italian defender Marco Materazzi who had apparently insulted his family. Zidane was sent off and France subsequently lost the match.
On show in the courtyard of the Collection Lambert until June 2017, the powerful 5 metre / 16 foot high bronze sculpture is the work of the French-Algerian artist Adel Abdessemed.
Also at the gallery this winter: some choice 19th and early 20th century masterpieces on loan from Avignon's Musée Angladon, which is temporarily closed for renovation.
Some two dozen works by artists including Van Gogh, Chardin, Cézanne, Degas, Picasso, Modigliani, Man Ray and Vuillard are on display alongside the Lambert's own cutting edge contemporary pieces, until 26 February 2017.
During its own recent building works, the Collection Lambert continued to stage shows at other venues. In 2013, Les Papesses (The Female Popes) was a celebration of Louise Bourgeois, Camille Claudel, Kiki Smith and other transgressive female artists - in the setting of the Palais des Papes.
Its big exhibition of 2014 was La Disparition des lucioles (The Disappearance of the Fireflies), which took place at Sainte Anne, a former prison dating back to the 18th century.
The curious title of the show was inspired by a famous text published by the writer and film-maker Pier Paolo Pasolini in 1975 and it explored themes of imprisonment, the passing of time, solitude and love.
Public taste is sometimes hard to predict: the apparently attractive Papesses show was a relative flop, but The Disappearance of the Fireflies turned out to be a huge and unexpected success.
So much so that the brooding setting of the Sainte Anne prison may be later converted into a yet another permanent exhibition space in Avignon, alongside the main museum.
If and when that happens, it will confirm the city as one of France's most exciting centres of contemporary art.
Where: Collection Lambert, 5 rue Violette, 84000 Avignon. Tel: (+33) 4 90 16 56 20. Website for the Collection Lambert
Note that the Hôtel de Caumont is not to be confused with the similar-sounding Caumont Centre d'Art gallery in Aix en Provence!
If you are planning to visit more than one museum or tourist sight during your stay, be sure to pick up the "Avignon Passion" pass.
Ask for it on your first visit to a local monument and you will get discounts of between 10% and 50% to subsequent attractions both in Avignon itself and in Villeneuve.
The card is valid for 15 days and can apply to up to five persons. More details from the Avignon Tourist Office.
Photo credits (from top): © SJ for Marvellous Provence (two images), Collection Lambert, SJ for Marvellous Provence, Collection Lambert.