The Duna di Feniglia Nature Reserve is a state protected natural area established in 1971.
The Feniglia is a tombolo or a strip of sand between the hill of Ansedonia to the east and Monte Argentario to the west. It is about 6 km long and covers a total area of 474 hectares. From Orbetello, the Feniglia Dune can be reached by the Leopoldian Dam, while from Ansedonia it can be reached by taking the Aurelia state road and then taking the municipal road that derives from it. The reserve is crossed by an unpaved road that can be travelled on foot, by bicycle (it is closed to urban traffic), built between 1928 and 1940.
In 1971, by decree of the Ministry of Agriculture and Forestry, the Feniglia dune was declared a Forest Protection Reserve because of the important functions it performs.
The Feniglia dune is divided into three strips of vegetation that extend parallel from the sea inland, on the lagoon. The first is the protection strip, covers an area of 94 hectares and overlooks the sea, consisting of vegetation typically coastal, the second extends for 320 hectares and is mainly occupied by a forest of domestic pine adult, the third, covered by domestic pine and broadleaf, has an area of 60 hectares and has an outlet on the Lagoon of Orbetello.
The fauna of the reserve consists of badger, fox, stone marten, weasel, skunk. The fallow deer is fundamental because it places a limit on the spread of invasive broad-leaved trees. Among the bird species: the green woodpecker, the hoopoe, the turtledove, the blackbird, the jay, the cuckoo. In the wetlands there are interesting species: the grey heron, the egret, the teal, the wigeon, the mallard, the garganey, the coot, the stingray, the gossip, the marshmallow, the black squid, the sandpipers and the godwit.
Access to the reserve is free on foot and by bicycle along a road of about 6 km. Along the way, at intervals of about 1 km, there are milestones and information panels that indicate the outings to sea that lead to the beach. Inside the reserve, on the lagoon side, there are some ornithological observatories, a nature trail for the blind and a fitness trail.