The IGN TOP 25 hiking map No. 2104 ET covers the following area: Boulogne-sur-Mer, Boulonnais Forests, Caps & Marais d'Opale Regional Nature Park.
- Contour lines at 10-metre intervals.
- Detailed legend: vegetation, rocks, transport routes down to the smallest paths, buildings down to individual sheds, woodland, isolated trees, rivers, springs and more.
- Waymarked trails and tourist information are shown.
- Scale: 1:25,000 (1 cm = 250 m).
Municipalities covered: Boulogne-sur-Mer, Baincthun, Hesdin-l'Abbé, Saint-Étienne-au-Mont, Hermelinghen, Desvres, Saint-Martin-Boulogne, Rety, Wirwignes, Wimille, Belle-et-Houllefort, Alembon, Dannes, Maninghen-Henne, Boursin, Colembert, Outreau, Le Wast, Hubersent, Doudeauville, Longfossé.
Places to discover: PNR Caps et marais d'Opale, Pointe aux Oies, Rochers du Fort Croi, Dunes de la Slack, Collines du Boulonnais, les Dunes, Maison du Parc, Casino, Pont de Briques Castle, Basilique Crypte, Souverain Moulin Castle, Fort Mahon, Manoir de la Haye, Colonne de la Grande Armée, Nausicaa aquarium Boulogne, Lozembrune Castle.