The Special Protection Zone "Viadana, Portiolo San Benedetto Po, Ostiglia" is divided into four large territories - only partially belonging to the territory of Oltrepò - and belongs to the European Ecological Network Natura 2000.
With more than 7,000 hectares of land, it is the largest protected area of the Park System of the Oltrepò Mantovano and encloses all natural expressions (running water, sand, riverbeds, riparian forests) and anthropic (poplar groves, arable land, sand and clay quarries, hydraulic defenses, river entrances, urban settlements, civil and industrial infrastructures) typical of the lower course of the Po river which, with its floodplains, is the largest area with widespread nature of Mantua territory and, more generally, of the Padana Plain. It is not surprising, then, the wildlife wealth of the Special Protection Zone (ZPS), especially with regard to birds (over 200 species), including the black kite, the osprey, Montagu's harrier, the bee-eater, the little ringed plover, the common tern, the little tern, the woodcock and the golden oriole. Among the mammals, in addition to the hedgehog, hare, weasel and numerous species of small rodents, you will find the badger and the roe deer. Among amphibians and reptiles, crested and spotted newt, green frog, the tree frog and common and green toads, besides the green lizard, green whip snakes and grass snake. Among the fishes, finally, the increasingly rare sturgeon, the flathead mullet, the eel, the twait shad, the carp and the wels catfish (a danubian species exceeding two meters in length, which is creating a lot of problems to local fishes). The areas close to the river provide suggestive views and can be reached, according to the water levels of the period, by means of an extensive network of service roads. Among these, there are also some "towpaths": roads that run along the sides of the shores, which were used to tow boats upstream. Access to motorized vehicles is permitted only in sections indicated by appropriate signals. The four areas of the ZPS are connected through paths EuroVelo EV8 and cycle road 2d and 2s of the Province of Mantua. They are also connected to the protected areas of the Park System of the Oltrepò Mantovano through the Park Cycle route.