The Manifattura dei Marinati is a working museum occupying the historic eel processing plant on the canal just behind the Trepponti bridge. Comacchio's economy for centuries depended on the eels caught in the surrounding valley lagoons — the Valle di Comacchio is one of the most productive eel habitats in Europe — and this building is where they were cleaned, roasted on large iron spits, and preserved in vinegar marinade for export across Italy and beyond.
The museum preserves the original equipment: the great copper cauldrons, the wooden racks, the stone ovens, and the terracotta storage vessels. Guides (Italian-language; ask about English options at the tourist office) explain the entire process from catch to jar. The museum is open most of the year and the building itself, with its long canal-side loggia, is one of the most atmospheric in Comacchio. The onsite shop sells the marinated eels if you want to judge the result directly.