The Vallette di Ostellato are a complex of forests and freshwater marshes: 15 kilometers included between two large drainage canals. The trail starts from the Nature Village and is about 4.5 kilometers long; it can be traveled on foot, by bicycle, by electric vehicles or by car; at the end of the trail it is possible to continue further, only on foot, among patches of blackthorn, elderberry and tamarisk, toward Valle Zagno. In this better preserved and protected part, there are a number of birdwatching observatories, consisting of both screens and huts.

One of the main observatories is near the aviary of white storks, another overlooks a clear of the marsh, from which nesting of penduline, great crested grebe and grey heron can be observed.

The Vallette are a good year-round avifauna observation point; they are home to all species of European herons, numerous species of ducks and waders, including numerous black-winged stilts, and the aforementioned nucleus of white storks.