Life is art in Nantes this summer as Estuaire, an ambitious five-year project to create a cultural route from the city along the Loire estuary to the sea at Saint-Nazaire, heads towards its conclusion. And now a temporary trail, Le Voyage à Nantes, has opened, challenging locals and visitors to take a fresh perspective on this French city in the west of the Pays de la Loire. A pink line painted on the ground leads to classic cultural sights, many of which provide the context for contemporary art installations. On 19 August, many of these new works will vanish, but the pink line will remain as a permanent cultural tour. This walk picks out just some of the highlights of this free trail.
Start at Le Lieu Unique (00 33 2 40 12 14 34; www.lelieuunique.com; free), a former biscuit factory that recalls Nantes' industrial past, now a national arts centre. It's currently hosting "Playgrounds", a sequence of fun installations by young local architects, such as "You Always Win", where visitors are equipped with 3D glasses and a basketball to shoot through a virtual hoop.
Turn left and pick up the pink line over the tram tracks to Rue Henri IV. Where the pink line turns right again, head left into the gardens of the 15th-century Cathédrale Saint Pierre et Saint Paul (admission free). Step within its bright limestone walls to see the Tomb of King François II, on which lie life-size marble images of the Duke of Brittany and his wife, Marguerite de Foix.
Go left out of the cathedral entrance and pick up the pink line along the Rue Mathelin Rodier, following it briefly into the heart of the medieval quarter to the west entrance of the Château des Ducs de Bretagne (00 33 2 40 48 62 81; www.chateau-nantes.fr; free), an impressive granite fortification, that recalls the importance of this city to the powerful Dukes of Brittany in medieval times. Enter the courtyard to discover a huddle of buildings, dating from the 15th to 18th century, hewn from more of that white limestone. They house the Nantes History Museum (€5), where you can explore the city's story.
At the west entrance, turn left and then right on to Allée du Port-Maillard. Continue forward to the Place du Bouffay. At the centre of this square, a prime example of the grand designs of the architects who expanded the city to the west in the 18th and 19th centuries, is the audacious "Monte-Meubles L'Ultime Déménagement". For this bizarre installation, artist Leandro Erlich has created a section of a grand house that appears to float 30 feet in the air, with a motionless electric staircase, bearing a pile of furniture, attached to its open window.
Follow the tram tracks west to Place du Commerce, then head north through the square to Place Royale. "Outdoor Playground Mont Royal(e)", a humorous take on Mont Gerbier des Joncs, the source of the Loire, envelops the central fountain. Use the footholds on its walls to scramble to its summit or go "caving" within to find the spring at its core.
Exit the from square onto Rue de la Fosse, following the pink line to the Passage Pommeraye. Take the central staircase and rise through this most graceful of 19th-century arcades, with its galleries of shops. Stop by "Des Chambres en Ville", a recreation of the television shop once owned by the film director Jacques Demy, which also featured in his film, Une Chambre en Ville.
Leave the arcade and follow the pink line along Rue Crébillon to Place Graslin. Check out La Cigale (00 33 2 51 84 94 94; www.lacigale.com), a 19th-century restaurant with extravagant Art Nouveau interiors, which serves some of the freshest seafood in town – a good lunch stop. The main sight in this square is the 18th-century Théâtre Graslin, but its glorious façade of Corinthian columns, topped with statues of the muses, is currently obscured by scaffolding.
Follow the pink line out of the square along Rue Piron to Quai de la Fosse. Turn right, continuing until you spot "Plateformes Points de Vue", a walkway suspended above the pavement covered in shards of Perspex, which you can explore via a staircase. Cross the road to the Mémorial de l'abolition de l'esclavage (00 33 2 51 17 49 48; memorial.nantes.fr; admission free). Take the steps down to this moving exhibition, which reveals the city's role as France's main slave port.
Continue west along the line and cross the Loire at Pont Anne de Bretagne to the Ile de Nantes – these disused docks are fast becoming the city's avant-garde neighbourhood. Many of the most unusual artworks of the trail are on this island, just follow the pink line to find them. But for the final call, turn right as you leave the bridge into the Parc des Chantiers.
This is the home of Les Machines de L'Ile (00 33 2 51 17 49 89; lesmachines-nantes.fr), where nature is explored through astonishing feats of engineering. Most magnificent is The Great Elephant, a 45ft-high mechanical wooden pachyderm that takes up to 49 passengers a time around the park, spraying water from its trunk (€7). After all that walking, it's a great way to take the weight off your feet.
Check in to Sozo Hotel (00 33 2 51 82 40 00; sozo hotel.fr), a new boutique stopover set in a 19th-century chapel, next to the city's botanic gardens. The original fabric of the building – stone walls, vaulted ceilings and stained-glass windows – provides an attractive historic frame for sharp minimalist styling in the 28 comfortable bedrooms. From €143 (£115) per room per night in July.
Red and black are the bold choice of colours at flamboyant new restaurant and skybar Vertigo (00 33 2 51 82 70 44; vertigo-restaurant.com). Located at the top of a modern tower block in the Ile de Nantes, diners enjoy panoramic views, and dressy dishes such as braised John Dory with carrot and fennel purée and turmeric emulsion. Mains from around €19 (£15).
Kate Simon visited Nantes as a guest of Nantes Tourisme (00 33 892 464 044; nantes-tourisme.com). She flew from London City airport to Nantes courtesy of Air France (0871 66 33 777; airfrance.co.uk), which has return flights from £217 in July. Nantes Atlantique airport is also served direct from the UK by Air France from Southampton; easyJet (0843 104 5000; easyjet.com) from Gatwick; and Flybe (0871 700 2000; flybe.com) from Gatwick and Manchester. The airport is a 15-minute drive from the city centre. The taxi fare costs €25-€35. Alternatively, the Tan Air Shuttle operates every 30 minutes between 5.30am and 11.15pm, Mondays to Saturdays, and 6.15am- 11.15pm on Sundays. The journey takes around 20 minutes and it costs €7.50 (£6). By rail, Eurostar runs from London St Pancras, Ashford and Ebbsfleet via Paris (where a change of station is required) or Lille, to Nantes in around six hours, with typical return fares in July around £199.
The city is easy to walk around and has a good tram service. Fares from €1.50 (£1.20) for one hour payable at ticket machines at the stops. A Pass Nantes (00 33 2 72 64 04 79; nantes-tourisme.com) costs from €25 (£20) a day and includes travel on public transport, entry to 30 top attractions, and discounts on shopping and leisure. Le Voyage à Nantes (00 33 892 464 044; www.levoyageanantes.fr) Estuaire (00 33 2 40 75 75 07; www.estuaire.info).