The Cornate and Fosini Nature Reserve is a protected natural area of the Region Tuscany established in 1996. It occupies an area of 879 ha inside the Municipality of Montieri in the northern part of the Province of Grosseto and the Municipality of Radicondoli in the Province of Siena. "Cornate and Fosini" is also a site of regional interest (SIR), due to the presence of rare and endemic species in the limestone prairies. The SIR includes the river ecosystem of the Pavone stream in excellent state of conservation. The geomorphological structure of the reserve is characterized by mountains, mostly covered by forest of natural origin (Turkey oak woods , chestnut woods, hop hornbeam woods) and reforestation of black pines; significant extensions of secondary prairies like garrigue and shrub land; relevant rocky outcrops, rivers with riparian vegetation and gorges.

The Cornate of Gerfalco is a limestone mountain that extends for about 4 km, is formed by seven peaks which increases until reaching the maximum height of m. 1059 s.l.m. in the so-called "Poggio Alto". Once, it was almost completely bare of vegetation showing the characteristic appearance of karst mountains. After reforestation, carried out in the '30s, its appearance has gradually changed and today it is almost completely covered with black pines and holm oaks in the Southern part and juniper, manna ash, hornbeams and maples in the Northern part.

From the top of the mountains, you can enjoy a wonderful landscape: from the South side, a thick forest of Turkey oaks until Massa Marittima and the marine background of the gulfs of Baratti and Follonica; from the South-East part, the mountain of Poggio di Montieri and the mountain of Prata; from the West side, the boraciferous chimneys of Monterotondo Marittimo, Castelnuovo Val di Cecina and Larderello; from the North-East side, the town of Siena where, on clear days, you can easily see the Dome and the Tower of Mangia; from the North-East side, the "Carline", an area renowned for trekking walks and horseback rides, rich in vegetation and fresh water springs. The predominant vegetation of the "Carline" are: black pines, white firs, American firs, chestnuts, Turkey oaks, oaks, mountain maples, broom, juniper, alborello, as well as several wild fruit plants. In spring and summer, a fresh mistral wind blows, spreading nature scents in the peaceful and uncontaminated environment.

From the top of the mountains, you can enjoy a wonderful landscape: from the South side, a thick forest of Turkey oaks until Massa Marittima and the marine background of the gulfs of Baratti and Follonica; from the South-East part, the mountain of Poggio di Montieri and the mountain of Prata; from the West side, the boraciferous chimneys of Monterotondo Marittimo, Castelnuovo Val di Cecina and Larderello; from the North-East side, the town of Siena where, on clear days, you can easily see the Dome and the Tower of Mangia; from the North-East side, the "Carline", an area renowned for trekking walks and horseback rides, rich in vegetation and fresh water springs. The predominant vegetation of the "Carline" are: black pines, white firs, American firs, chestnuts, Turkey oaks, oaks, mountain maples, broom, juniper, alborello, as well as several wild fruit plants. In spring and summer, a fresh mistral wind blows, spreading nature scents in the peaceful and uncontaminated environment.

From the top of the mountains, you can enjoy a wonderful landscape: from the South side, a thick forest of Turkey oaks until Massa Marittima and the marine background of the gulfs of Baratti and Follonica; from the South-East part, the mountain of Poggio di Montieri and the mountain of Prata; from the West side, the boraciferous chimneys of Monterotondo Marittimo, Castelnuovo Val di Cecina and Larderello; from the North-East side, the town of Siena where, on clear days, you can easily see the Dome and the Tower of Mangia; from the North-East side, the "Carline", an area renowned for trekking walks and horseback rides, rich in vegetation and fresh water springs. The predominant vegetation of the "Carline" are: black pines, white firs, American firs, chestnuts, Turkey oaks, oaks, mountain maples, broom, juniper, alborello, as well as several wild fruit plants. In spring and summer, a fresh mistral wind blows, spreading nature scents in the peaceful and uncontaminated environment.

In the North-West side of the Mountain of Cornate, the characteristic red ammonite marble was extracted and even used to decorate the architectural parts of the Duomo of Siena. Moving to the South, at the limits of the province of Grosseto, on the border with the province of Siena, stands the "Poggio di Mutti" limestone hill, which is linked to the Eocene limestone that extends towards the South until the torrent "Pavone"..

The Castle of Fosini was built at 639 meters above sea level under the promontory of the mountain chain of Cornate of Gerfalco. It is a mighty fortification perched on a limestone spur overlooking the valley of the Pavone stream, overhanging on the narrow Rio Riponti gorge. Its structure has a quadrangular shape arranged around a central courtyard. The façade was restored in a post-medieval period, using brick elements and ammonitic red marble coming from the nearby Cornate. Overall, the structure shows signs and damages of different ages, which determine the need of urgent care to bring the manor back to its former glory.

It was built around the tenth century, to guard the silver mines scattered in the nearby area of Poggio Mutti. It was fortified around 1100 by the counts Pannocchieschi; later, it was owned by the Bishops of Volterra and then subjugated to the Republic of Siena, when it counted a population of about 300 people. In 1340, it returned under the dominion of the powerful Pannocchieschi family, rich feudal lords of the County of Elci, who owned over 30 castles and numerous possessions in Volterra territory. At the beginning of the twentieth century, it was transformed into a farm by the Baroni Sergardi's dynasty, from Siena.

Throughout its history, the castle has undergone several changes with addition of rooms and architectural elements according to the taste of the period in which they were performed. It still preserves the square keep, the main tower and the belvedere that sweeps over beautiful and evocative panoramas. The building walls and surrounding walls in the South-West side are the most damaged, they overlook the steep limestone rocks and are a shelter and ideal place for nesting of rare birds of prey such as the Peregrine Falcon and the Lanner Falcon. Some studies suggest that the name of the castle may come from the Etruscan term 'Eusinies', in Latin 'Fosinius', referring to the activity of the several metallurgical forges (Fuxine) present in the area up to the medieval period.

Like any self-respecting ancient manor, even the Castle of Fosini has its legendary ghost. The story tells about Ilario Brandani, known as necromancer and connoisseur of ancient formulas to evoke the dead souls. He lived in the castle around 1400, just in the years when an epidemic of plague struck a large part of Central Italy. He was the only survivor to the disease and continued to live alone in the castle in the grip of madness, among dozens of corpses. It is said that, after his death, his ghost remained imprisoned within the walls of the manor, has long wandered in those creepy places and still continues to hover, condemned to the eternal search for his companions.

In front of the castle, under the shade of centenary lime trees, there is an ancient recently restored fountain, where fresh spring water gushes.

Not far away from the Castle, you can admire the millenary and still vigorous "Chestnut Tree of Fosini". The Geopark of Colline Metallifere .