Boulogne-sur-Mer is a city, known as a major fishing port, on the north coast of France. By the port, Nausicaá is a huge aquarium with thousands of marine species. In the fortified old town, Notre-Dame Basilica has an ornate crypt. The city’s 12th-century belfry was the keep of a Norman-era castle. Ancient Egyptian and Greek artifacts are on display at the Castle Museum, which is set within a 13th-century chateau.