The medieval ramparts of Boulogne's Haute Ville form a complete rectangle about two kilometres in circuit, and the entire circuit can be walked along the top. The walls date from the 13th century and are among the most complete surviving examples of medieval fortification in northern France. Four towers punctuate the corners; a fifth, the belfry, rises from the interior.
The rampart walk is free, takes about 45 minutes at a leisurely pace, and offers the best perspectives on the town and harbour. The views north toward the Channel and the white cliffs of Cap Gris-Nez are particularly good in clear weather. Enter via any of the four gates; the main entrance from the lower town is the Porte des Degrés on the eastern side.