The plane flew in over the Loire estuary, then landed, always a good result. "Welcome to Nantes Atlantique Airport" cried the air hostess. My heart raced. Nantes, once capital of Brittany, is now not in Brittany at all. Home to mechanical elephants, biscuits and muscadet wine. I stood up sharply, cracked my head on the overhead locker, collapsed back, came round, and said: "It's been so long"

"Since what?" said my wife. "Since I stood up so fast," I said.

"Tell me all you know about Nantes," I said in the subsequent taxi. "Was a big port once," she said. "We have five cathedrals," chipped in the taxi driver, which indicates that you should never trust taxi drivers. They run cars, not research institutes. Nantes has one cathedral and it has been shut since someone tried to burn it down in 2022.

Direction-wise, though, the driver nailed it, dropping us off at exactly the hotel we had booked. On Rue Crébillon, the poshest shopping street in town. It's in this sector that Nantes translated riches from the slave trade into neo-classical edifices and promenades. You would expect a brace of Bennetts, a Darcy or a Dashwood along, and maybe fewer tattoos.

The hotel staff exhibited Canadian levels of pleasantness, and we settled in the bar. "What you need to know about Nantes is," I said, "that it's had a grand past, got quite a lot wrong and has now got almost everything right." "Ah," she said. With muscadet finished, we went out to continue her education about her own country. She appreciates this.

After times as capital of the independent duchy of Brittany (see the chateau), Nantes grew into a great port, busy ship-builder and baker of biscuits through the 17th to 19th centuries. The 20th was trickier. The port shut in 1987. Nantes lost its way, then found it again through culture. There is fun stuff punctuating the public spaces, informing the atmosphere and surprising you at several turns. It keeps you smiling. This may be the most playful city in France.

For a start, they've got the 50-tonne elephant, a three-times normal size monster of wood and steel from the Machines de l'Île workshops. It's driven by a hybrid electric motor, but absolutely alive: majestic, rivetingly huge, rising above the surroundings to some realm of reality where da Vinci, Tolkien and Brunel all work together. Fifty people may climb aboard for a 30-minute stomp round. I can think of few other cities where someone says: "May we have space to build a 40-foot high, 70-foot long elephant, please" - and the authorities say: "But of course."

On the river island itself, they are slotting contemporary life into superannuated industrial surroundings. The old banana warehouse is colonised by bars, restaurants and galleries: perfect revenge on the frightful fruit. There are playgrounds and roundabouts, 18 big rings (by Daniel Buren) on the river's edge (for no particular reason), a British zebra crossing with Belisha beacons, and a gigantic measuring tape unravelling round an office courtyard. This sort of thing doesn't half cheer up a townscape.

And it continues back in the centre. They've pulled out traffic, opened up great spaces and put in left-field statuary - a young girl escaping from her plinth, an ordinary bloke stepping into thin air off his - and greenery by the park-full. At some point, we wandered into the medieval Bouffay district, where snaking streets hosted a UN of restaurants and we ate Thai, which could have been spicier but was pretty good all the same.

Here was evidence that Nantes had had a certain friskiness even before the recent renaissance. How could it not have? Jules Verne was a native, and there is no more brazen brasserie in France than La Cigale, opened in 1895. It's as if every item of Art Nouveau - glazed tiles, mirrors, sculptures, ochre, gold, glass - has been swept up and thrown in. "Effusive" doesn't get close. It needs setting to music by Offenbach. The food is terrific, too.

And, just down the street, the Passage Pommeraye remains the fanciest shopping arcade in France. Overspilling with baroque on three levels, it recalls an age when recreational retail was an expression of civilised behaviour not accessible to the rabble.

There is elegance in abundance ll over the place, not least in parades of town houses which look dignified enough to house a Crawley or a Bridgerton. But they come with a subplot. Nantes grew rich, in part at least, because it brought intensity to the slave traade. City ships carried some 550,000 African men, women and children to the Americas.

Nantes "looks this past square in the face", as city literature says, and a memorial to the abolition of slavery opened in 2012. For 400 metres along the quay from which slavers set out, 2,000 light plaques set in the pavement recall the names of the ships. You then plunge underground into a 90-metre gallery, intended to evoke the wretched below-decks conditions which killed 13 per cent of slaves during the voyage. It talks of slavery, of those who profited, and of those fought for abolition in French colonies. (It came in 1848, 15 years after Britain.)

The mea culpa continues in the Château des Ducs de Bretagne (Dukes of Brittany castle), which retains a monumental presence sufficient to rule a region or two. Within, the museum delivers history with a hum, not the usual dull drone, devoting much space to all aspects of slavery. There is nothing like seeing the bills of sale (for humans), the irons and the neck-braces to render atrocity palpable. You know it in theory. This is about as close as you can now get in Europe to the practice. "Overwhelming," said my wife.

So we went for a drink. There's a bar across the way in what used to be the LU biscuit factory. Nantes became big in biscuits with the sugar brought back from the Americas after slaves were sold. (If you've been to France and bought Petit Beurre or BN biscuits, you're in the loop.) Biscuit making is now out of town, so the factory is, as you'd expect, a hip cultural centre. You can't miss it. It's topped by an exuberant tower, like something a six-year-old might have baked helping mummy in the kitchen. Mummy would then have thrown it away.

But the beer was fine, and we talked of Anne de Bretagne, duchess of Brittany and the greatest of Breton women, twice queen of France, woman of innumerable pregnancies and dead at 37 in 1514. She had treasured the castle and would have been apoplectic that, administratively-speaking, Nantes is not even in Brittany these days. It's the capital of the Pays-de-la-Loire region. Certain Breton-leaning locals think this an outrage. They clamour to be Breton. Others make less fuss.

We romped around splendid parks and gardens and rode the trams (free at weekends), and one morning took a two-and-a-half hour cruise down the Loire estuary to St Nazaire. The banks were punctuated with more massive artworks: an entire house tilting into the river, a yacht apparently melting over lock-gates, and several exotic animal sculptures. As a serious ship-building port, St Nazaire had the expected pharaonic tangle of buildings, quays and vast cranes so that one hardly noticed the 6,000-passenger cruise ship they are presently building.

The glowering old Nazi submarine bunkers survive, too. They couldn't not survive; so titanically sturdy is their concrete that blowing them up would take out most of western France. They now host Escal'Atlantic, a terrific exhibition-cum-stroll through the great days of transatlantic liners - many of them, like Le Normandie, Le France and Queen Mary 2, built in St Nazaire.

Back in Nantes, we slipped into the Univers bar. It is said that, in 1918, France heard its first notes of jazz in this very bar, courtesy of Jim Reese Europe's US navy "Hellfighters" band. I don't doubt this for a second. We crossed Place Graslin for a third meal at La Cigale. When faced with France's most famous brasserie, you dive in. I'd return tonight if I wasn't 500 miles away.

Later we strolled narrow streets and unexpected squares whose terraces throbbed with laughter, life and students being loud. We ended up at Le Mac Irish bar. I asked for a peaty, smoky single malt, the waiter brought Kilchoman and I decided we had better extend our short break by a month. Maybe two.

Ryanair flies to Nantes from Bournemouth, Edinburgh, Stansted and Manchester (ryanair.com), Easyjet from Bristol and Gatwick (easyjet.com).

Best address in town, and surely the friendliest, is the Oceania Hotel de France (www.oceaniahotels.com; room-only doubles from £75).