The Belfry of Boulogne is the Haute Ville's oldest surviving structure, a solid 12th-century tower that has accumulated uses over the centuries — castle keep, dungeon, chapel, watchtower — before becoming the civic symbol it is today. The tower stands 47 metres high and can be climbed via internal stairs; from the top, the views over the old town, the harbour, and the Channel are exceptional.
Entry is free and the tower is usually open daily in summer months. The belfry is separate from the basilica dome that now dominates the Haute Ville skyline — the two structures stand close together but are centuries apart in age and character. For historical context, the belfry is the more interesting of the two.