The Rialto Bridge will be particularly crowded at dusk, so my advice is to reach the Fondaco Rooftop Terrace. The terrace is on the roof of a luxury multi-story shopping mall, but it's well worth reaching for a spectacular view of the Grand Canal. Furthermore, the visit is completely free, but the time of the ascent must be booked, you can find the link below.
Allez consulter mon guide pour les meilleures choses gratuites à faire ainsi que des itinéraires et des conseils de voyage pour rendre votre voyage inoubliable.