Diaccia Botrona Natural Preserve spreads over more than one thousand hectares of land and is considers the most significant Italian humid area (it has been considered internationally important as of 1991). It was instituted in 1996, and represents what remains of the old Prile Lake (Lago Prile), which covered a territory of fifty squared kilometres and was drained in the 18th century.
The actual marsh occupies approximately seven hundred hectares, next to Castiglione della Pescaia pine wood, and stretches up to the plain which links this sea side resort with Grosseto. Diaccia Botrona preserve includes a rare ecosystem, with an incredible variety of living micro organisms, both concerning the flora and the fauna. It is a genetic bank which contributes to the biodiversity of the area.

Among the flora, one can see salt wort groves (in the West side of the preserve) and lemon groves. The type of vegetation typical of the marsh is characterised by rushes and carexes, along with around fifteen types of orchids. Ash trees, and elms can instead be admired in the vast forest which once covered the majority of the maremman plain. Avifauna is also particularly interesting: there are ospreys, falcons of the marshes, white herons, red herons, marine jays, cookoes, and herons (garzette). Foxes, porcupines, hedgehogs, badgers, hares and nutrias, are among the main mammals which live in the preserve. Among the reptiles, the main ones are the turtle of the marshes, rat snake, green lizard, lizard and gecko. There are also many insects, shellfish, annelids and arachnids.