Climb the 15th-century clock tower in the Rue de l'Horloge or visit Le Jardin Anglais, in front of the 12th-century Basilique Saint-Saveur, for a good view over the river, the small port, and the viaduct.
You can view the river, the small port, and the viaduct from the top of the clock tower at the Rue de l'Horloge.