Boulogne-sur-Mer, the largest Roman port in north-west of Europe, has retained a remarkable architectural heritage. Gateway to England, the town built up its fortifications on the foundations of a Roman enclosure. Go up the Grande Rue, the main street linking the upper and lower town, and take the path along the ramparts, a superb stroll. Go back down via the Porte de Calais, a fortified gateway. Here you find yourself in front of the basilica dedicated to Our Lady, an audacious piece of architecture topped by a dome which has become the symbolic beacon of the town. Restored painted décor and treasures in stone are revealed in its crypt which is the largest in France. Two streets along, the castle, built in the 13th century, and now a museum, will guide you well beyond local history.