The city, faithful to the Pisan Republic, defended by strong walls and protected by the waters of the River Serezza and the Arno, had endured nine months of siege in which assaults carried out with bombards, catapults, mobile towers and rams followed, but in the end he gave up on hunger. The Florentines thus came into possession of a center on the banks of the Arno from which river trade and the nearby branch of the Via Francigena dominated, controlling the flows of pilgrims, merchants and the prosperous countryside around the slopes of Mount Pisano. With the fall into the hands of Florence it was thought to reinforce this important conquest to discourage the sights of the neighbors. The decision was made to build a fortress that was impregnable and discouraged the pitfalls of the Visconti armies that threatened Tuscany from Lucca. The Florentine government commissioned the famous architect Filippo Brunelleschi to design the new defensive work. Brunelleschi’s proposal was immediately very innovative: at the presentation in front of the government commission which also included the young leader Francesco Sforza, thanks to a model in clay and wood, the famous architect convinced everyone for the innovative solutions designed.
To build the new work, the town of Vicopisano was heavily modified: the churches and palaces that were in the area of ​​the top of the Vico hill were largely demolished. Brunelleschi’s fortification incorporated the pre-existing Tower of S. Maria (12th century) into the new structures. The latter was transformed into the keep of the current fortress. The typology of the fortress is still medieval, with high crenellated walls resting on arches with seals to cast inflamed Greek pitch and hot oil on the attackers. But in the defensive complex there are also many innovations such as the abundant use of drawbridges intended, when withdrawn, to isolate the various parts of the fortress in case the enemy managed to penetrate it. For example, before entering the courtyard of the fortress, you had to conquer the front door equipped with a drawbridge and a moat. Inside, in case of loss of the courtyard, the defenders could break down the staircase resting on four slender arches that connects the courtyard with the patrol walkway. If the enemy had managed to reach the curtains, the defense would have stood in the tower: it was possible to isolate the tower from the rest of the fortification by withdrawing the drawbridge that connects the patrol path with the only entrance of the same. The tower, equipped with its own cistern and supplies of provisions, could still last for a long time.
The most ingenious solution designed by Brunelleschi is surely the mighty crenellated wall that descends from the Rocca to the foot of the Colle, where it ends with the high Soccorso tower (21 m) built near the Arno, which at that time passed right under the walls of Vicopisano. As the name of the tower suggests, this work was intended to avoid isolation in the event of a siege by guaranteeing the supply of food, weapons and reinforcements by river in the event of a siege.
The boats could land in a cove, defended by fortifications that have now disappeared, unload men and dust that were brought in by a narrow hatch, then they went up to the second floor of the tower, to access the wall and climb to the Rocca. But Brunelleschi had thought of everything: in fact, if the enemy had succeeded in conquering the Torre del Soccorso and had tried to access the fortress from the wall, he would have found himself exposed to the pull shot from the Rocca, but above all he would have found the connection between the wall and the patrol path of the curtains of the Rocca from another drawbridge, which opened a passage of about three meters on a cliff of fifteen meters. Today the Pisan flag is flying over the tower of the fortress, but there are no winds of war, only visitors who climb to the top of the fortress to admire the view.
(from leviedelbrigante.it)

History

The structure of the fortress was of crucial importance for the Pisan Republic, perpetually at war with Florence. The castle was the nucleus of a system of fortifications scattered over the surrounding area, among which we can list the castles of Caprona, Vicopisano and Buti. The communications between these outposts and the fortress, as well as those between the fortress and the city of Pisa, took place with sheets, banners, smoke, fires or artillery shots through a code that allowed the sudden information on the movements of the approaching enemy troops. In case of poor visibility, the signal was passed through the various towers located on the Pisan mountains: the Torre dello Spuntone, the castle of Asciano, the castle of Agnano and the castle of San Giuliano.

Theater of bloody battles between Pisans and Florentines, it was repeatedly a stronghold of the former when the city had now fallen into the hands of the enemy. The site was already occupied by a fortification from 780, but the real fortress was built only in the 13th century, and survived as an active military structure until the final fall of Pisa in 1503. The last structures to be built, in view of the he last decisive confrontation with the Florentines were the four corner towers, two large eastern ones and two smaller western ones, with slits and crossbowmen.

In 1509, however, the fortress was renovated by Antonio da Sangallo, who is credited with the two polygonal bastions and by Luca del Caprina, from the Francione workshop, who is credited with the large cylindrical tower on one edge of the perimeter. The fortress was later abandoned as it lost its border position and therefore its defensive usefulness.
La Rocca della Verruca as it appeared in an 1875 painting by the painter Károly Markó the Younger.

In the early years of the twentieth century a project was started for the construction of a monumental cross, in response to the initiative of Pope Leo XIII to place the symbol of Christianity on the highest peaks in Italy. The first stone was laid by the Archbishop of Pisa Maffi in 1904, but the works did not continue due to the block imposed by the Superintendency of Cultural Heritage, determined to preserve the appearance of the ancient fortress.

On the evening of 8 September 2009 the north-western flank of the mountain was affected by a violent fire of arson, extending from the Nicosia di Calci area to reach Crespignano and Caprona, below, and Lombardone, near the top. The fire destroyed about 120 hectares of forest, leaving a wound in the panorama of the Pisan Mountains, visible from miles away. The municipality of Calci and the Province of Pisa, also given the scarce funding from the Tuscany Region, have decided not to intervene with reforestation plans, asserting that nature will take its course and thus favoring the growth of Mediterranean type, consisting of small shrubs and no longer of holm oak or oak woods.

Since November 2009 the Compagnia di Calci (an association founded in 2004 to protect the territory and the environment of Valgraziosa) has obtained, on loan for use by the owner Dr. Costantino Conforti, the part of the fortress that is located in the territory of the Municipality of Calci . The volunteers of the Association are constantly engaged in cleaning and safety works in order to safeguard the Verruca from the state of abandonment and in order to make visible to the numerous visitors the parts that the vegetation had covered over time. The vegetation surrounding the walls, composed of holm oaks, ivy, brambles and other shrubs, is seriously threatening the solidity of their foundations due to the action of the roots.

In September 2018 a very violent fire that devastated the south-eastern part of Monte Pisano, also hit the Rocca della Verruca, destroying practically all the surroundings.

Architecture

The stone and brick structure stands on a rocky spur and was rebuilt and enlarged at various times in the history of the Pisan Republic; these works were often carried out urgently in times of war, without careful planning. The ramparts and foundations, which cling directly to the underlying rock, are still firm, but the superstructures have collapsed almost entirely; some underground rooms and the central chapel, which preserves the four walls, remain almost intact.
Entrance of the Rocca

The plan of the complex is pentagonal, with the two eastern sides often considered as one very convex. Only four corners are fortified: the two facing north and north-east by round towers, the north-west by a bastion with a polygonal tip and the south-west by a slightly pronounced rampart.

The only entrance is located on the eastern side and is accessed via a short but steep staircase carved into the rock. Once through the door, which is currently damaged, the landscape opens onto the parade ground in the center of which are the remains of a church. In the ground there are several openings, some with steps and leading to underground rooms, others square in the center of the ceiling of the same rooms. Among the vegetation it is also possible to see the opening of a large quadrilateral cistern, with a barrel vault, now filled with debris and in the past probably used to collect rainwater.

The church, with a rectangular plan, preserves the mighty walls of large blocks of verrucana stone, on which two doors open on the longer sides and two splayed windows on the right side. The attentive observer can notice two distinct qualities of stone in the perimeter: large blocks up to two meters high, rows of a different quarry above. The latter probably come from the “Buca delle Fate”, a verrucano quarry which also provided the material for the construction of the church of the monastery of San Michele Arcangelo, not far from the fortress. Nothing remains of the roof and the floor, perhaps simply covered by the lawn.

Behind the ruins rise some large boulders which in the past were the support of the keep, of which only one wall remains and which probably extended up to the southern wall. Even today the highest point of the fortress (and of the mountain), the tower that stood there was probably dismantled with the advent of gunpowder, so as not to constitute an easy target for enemy broadcasts and, therefore, a danger to the besieged in case of collapse.

Most of the internal floor of the fortress is now covered with earth and grass, but still retains its characteristic slope towards the east. The south wall is therefore the highest part of the perimeter and on its internal face some of the stone corbels that served as a support for the internal walkways are still visible.

The south-east tower is equipped with two mines accessible via a stone ladder and equipped with fire mouths used to guard the southern and eastern walls with the entrance. The south-west bastion also has a mine, facing west, not raised and today without the stone frame, removed in the seventies. Near this bastion there is another mouth of fire to further monitor the south wall.

The north-west bastion has a large internal room, with vaults buried under piles of debris. Perhaps here was the entrance to the secret passage that led outside the structure, a sort of service or emergency exit. This structure probably fueled the rumor about the phantom underground tunnel that would have put Pisa in communication with the Verruca.

The well-preserved north-eastern tower is accessed via a stone staircase. Inside we find a rather large room with two fire mouths that had the task of guarding the northern and eastern walls. From the same staircase starts a narrow tunnel that ends with a fire mouth located in the middle of the east wall.

[text taken from wikipedia.it]

On the rocky spur above the town of Caprona stands the “Torre degli Upezzinghi”, a nineteenth-century copy of the tower of the ancient castle existing in the mid-eleventh century, mentioned by Dante (Inferno, XXI, 94-96) and dismantled by Florence in 1433. The tower commonly called “Torretta” is located on the top of a rocky spur, in a highly suggestive position overlooking the slopes of Mount Pisano. Today it is in a complete state of neglect and would need to be made safe.

The path winds along this stretch along the ancient Via dei Molini. Passing under the arches that connect the current villa to the old building on the banks of the stream, you can still see the wooden gears with vertical and horizontal axis that constituted the driving force of the Molino di Papo plant.