French national confidence is in sharp decline – but Paris 1900, an exhibition at the Petit Palais devoted to the capital's golden age, might reclaim some pride

It is 1900 in Paris and the "city of light" is at its most glittering. The "long depression" of the late 19th century is over, the horrors of the Great War are yet to come and la belle époque – as it would come to be known – is in full swing.

Fauré, Saint Saëns, Debussy and Ravel are making music; Rodin is working on The Thinker. Renoir, Monet, Cézanne, Pissarro and Degas are busy painting scenes depicting everyday life in the city; Pablo Picasso, recently arrived from Spain, is about to embark on his Blue Period.

By day, the Dreyfus affair still divides France and throws up new political movements. By night, the cabarets of Pigalle entertain absinthe drinkers and card players and Sarah Bernhardt captures hearts in the short "talking movie" Le Duel d'Hamlet.

Emile Zola is writing Travail (published the following year when his compatriot, Sully Prudhomme, was to win the first Nobel prize for literature) but has turned his hand to photographing the Universal Exhibition, the event that will capture the spirit of the new century and France's idea of itself as the cultural, innovative and inspiring centre of the new world. It is a period of peace and prosperity; France is confident, optimistic and looking outward on a sizeable empire (second only to Britain's).

This is still the city many foreigners imagine when they think of Paris. But it is a far cry from Paris 2014. The "temporary" Eiffel Tower, a relative novelty in 1900, may still be standing. There is peace and a certain prosperity in the Haussmann boulevards of chic arrondissements with their designer shops and Michelin-starred restaurants. But France is morose, inward looking, pessimistic by nature, unsure of itself and so lacking in confidence that even a teasing, if unflattering, photograph of its president on the front page of the Guardian can cause a national trauma and accusations of "le French bashing".

Enter Christophe Leribault, 49, the energetic new director of the Petit Palais and the man behind a new exhibition that will take the French capital back to its glorious past. Who? Where? Leribault is not a household name, even in France, and Le Petit Palais, officially the Paris Museum of Fine Arts, is only marginally so.

The museum, a stunning edifice built on the right bank of the Seine in 1900, is, as its name would suggest, overshadowed by its big sister next door, Le Grand Palais. Leribault, described by colleagues as looking like an "eternal adolescent", arrived at Le Petit Palais a year ago and decided that the very select and specific exhibitions it had organised until then were not going to put it on the tourist map, despite its location yards from the Champs Elysées.

The Paris 1900 exhibition, which will run from 2 April to 17 August, is the culmination of Leribault's efforts to get the museum noticed at home and abroad. This week he will travel to London to meet journalists to "create a buzz" around the event.

Leaping up from his desk to delve among the piles of catalogues in his office, Leribault hopes he will still have time to visit the Tate, the National Gallery and buy some art books during his cross-Channel day trip.

Paris 1900 will feature 600 exhibits as eclectic as la belle époque itself. There are, of course, the paintings, but also clothes, posters, photographs, films, furniture, jewellery, sculptures and even restaurant menus from the era.

It also promises "scientific and technical innovations, cultural effervescence and Parisian elegance".

The exhibition is arranged around the theme of the Universal Exhibition, entitled Paris, Window on the World.

Leribault admits that it has become a mythical era, but adds: "Paris is still living off that image. If you go to Japan or China, that is the picture people have of the city."

He added: "There was an atmosphere of optimism and life being one big party at the time. Of course, nobody imagined what would happen afterwards with the outbreak of the first world war. If they thought war would happen, they imagined it would be over quickly.

"French gastronomy was becoming more widely known and Paris was showing not just its cultural and inventive side, but its festive side. There was opera, theatre, circuses and Paris by night, including the maisons closes [brothels] and fashion.

"Paris was one great party. There was a spirit of confidence, of joie de vivre, with so many things going on at the same time. Even the future king of England came to Paris to enjoy himself. It was the capital of everything. It was one big party with elements of the funfair about it," Leribault adds.

Leribault is coming to London not just to sell the exhibition, but also Le Petit Palais itself, situated on Winston Churchill Avenue and long overlooked as a museum despite a major renovation seven years ago.

The Beaux Arts style building, designed by Charles Girault, was intended to be a temporary structure, like the Eiffel Tower, but won over Paris residents who refused to let it be torn down.

It has been nicknamed a "mini-Louvre" but without the crowds and the school groups, and with the bonus of free entry to the permanent exhibition, as well as a peaceful cafe and a beautiful garden. Leribault says that the new exhibition will remind Parisians, and foreign visitors, of what was, perhaps, one of the city's finest hours.

"La belle époque was very fluid artistically; there were lots of different movements and excesses. People were saying, 'we don't know where we are going but lots of things are happening and we are going to have pleasure and fun. We may even mock ourselves, that's how fun it is.'

"Of course, everything collapsed 14 years later with the outbreak of war. But in 1900 nobody had any idea of what was going to happen. In that sense it's a fascinating period."

He added: "And if the myth of la belle époque has endured until now, it's not just because of the contrast with the horror of the Great War that came after it, but because it is founded on a real cultural abundance."