Naours is the largest network of tunnels of Northern France. This "underground city" was a shelter for local populations through the centuries in times of conflicts. At its height, the underground city could host 3000 people.
During the first World War, British, Canadian and Australian soldiers visited these caves. They left over 3000 graffitis on the walls, still visible today.
The underground city also has a large park with the treetop adventure course.