Exploring the Opal Coast, from the Bay of Authie to the port of Calais

Though set inland, Montreuil-sur-Mer is an essential stop. You walk the ramparts of its medieval citadel, almost three kilometres long, with wide views across fields, copses and water meadows of the Canche valley. In the cobbled streets of Clape-en-Haut and Clape-en-Bas you notice tributes to Victor Hugo’s Les Misérables: the novelist set several scenes here after visiting in 1837. The Tourist and Heritage Centre offers a free heritage trail linking the Boulogne Gate, the Saint-Walloy Abbey and the market square –places that inspired Hugo to create Fantine’s birthplace, where Jean Valjean ran his glass-bead workshop.

Forty kilometres north, Boulogne-sur-Mer greets you with its mighty ramparts, medieval château-museum and the vast dome of the Basilica of Notre-Dame. Wander the old town before heading to Nausicaá, Europe’s largest aquarium. Inside you’ll come face to face with fluorescent jellyfish, shoals of sharks, bustling penguin colonies –a mesmerising glimpse into marine biodiversity. For lunch, book a table at La Matelote, famed for its local fish and shellfish dishes.

In Wimereux, the promenade keeps its Belle Époque feel with neat rows of blue and white beach huts. Families wander the promenade while kitesurfers zip across the waves. Walk on to Pointe aux Oies, where terns and kittiwakes patrol the cliffs. If you fancy joining the action, the local sailing club hires out windsurfing boards and offers lessons in the steady breeze.

The GR 120 trail links Cap Gris-Nez to Cap Blanc-Nez in a 15-kilometre walk (or seven kilometres if you start from Wissant). Gris-Nez is a low, dark headland of heath and rock, jutting into the Channel, where ferries pass close to shore. Blanc-Nez rises in gleaming chalk to 130 metres, with clear views across to the English coast on bright days. Along the way you’ll pass wartime bunkers, maritime beacons and seabird colonies clinging to the cliff face.

East of the regional park, Saint-Omer reveals a landscape shaped by water and Flemish history. Board a wooden bacôve, the traditional flat-bottomed boat, to glide among the market gardens and canals of the Audomarois marshes, where herons and dragonflies thrive. Back in town, visit the Gothic Notre-Dame Cathedral, then stop at the market for a crisp waffle or a shot of local gin.

At the northern end of the Opal Coast, Calais tells its story through lace – the city’s defining industry since the nineteenth century. At the Cité de la Dentelle et de la Mode, you watch Leavers looms in action and explore exhibitions linking lace to fashion and design. Temporary exhibitions look at the links between fashion, design and contemporary art.  From there, head to the Town Hall, topped with a 75-metre UNESCO-listed belfry, before stepping into the Musée des Beaux-Arts to admire works by Bourdelle, Rodin and Dubuffet. For lunch, Histoire Ancienne is a favourite spot where chef Patrick Comte serves classic regional cuisine.