There are many books about Zerba.

from the Books
The following articles have been taken from books, perhaps little known to most, written, it is perfectly understandable, by people who loved our areas, who have rigorously documented themselves and who have been able to describe what their hearts suggested.

taken from: Along the Trebbia - Mauro Busi and Andrea Chiari - DE AGOSTINI GEOGRAPHICAL INSTITUTE - 1987

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Val Boreca is found in Valsigiara, shortly after the town of Ottone, the reference town in the area.
Before a viaduct over the river, which replaces a bridge almost taken away by the flood in 1985, turn left, following the signs for Zerba.
The road of the Val Boreca proceeds towards the capital of Zerba, zigzagging through the trees of the forest until the view widens, just before the inhabited area of ​​Cerreto, on the gigantic green buttresses that rise on the southern flank. The imposing mountain range rises, entirely covered with woods, as compact as an immense wall of trees. In the middle of the ridge line emerges the tip of Monte Alfeo, the highest peak, where the snow lingers longer in spring. For a long stretch, not a house, not a sign of life interrupt this almost vertical curtain of woods, where only the furrows engraved by the streams are observed.
Suddenly, like a surprising vision, the town of Tartago appears, clinging to a fan that, freed from the woods, has been arranged in terraces. In this small triangle of lighter green the few houses of the village are grouped together. The singular spectacle is repeated for the more distant villages of Belnome and Artana, both of which stand out from the dense underworld of the wood with their plastered houses and the white bell tower of the church.
Continuing for Zerba and then for Vesimo, Pej and the Giovà pass, the road continues, always remaining on the hydrographic left of the stream, in a very different environment from the wild one on the other side, dominated by the green ridge of the Alpha: rock outcrops yellowish, within which the road seems to have been literally carved with a chisel, still inhabited villages, easy roads, reforestation of young conifers. Finally, on land free from the woods, the first appearances of those terraces, with a typically Ligurian flavor, which will be a constant in the landscape of the highest Trebbia valley. Here, on holidays and during the summer, it is easy to come across hikers and groups of riders (and cyclists ed.). To them, more than to the hasty cursors in the car, he will be able to fully appreciate the great beauty of this valley.
The Boreca valley represents, with its fifty-one square kilometers, the largest sub-basin of the Trebbia valley, after that, of course, of the Aveto which remains undisputed, the most important tributary.

The interest of the valley, however, does not lie so much in this quantitative element, but in the marked natural quality of its environment, among the most intact of all the Apennines. The presence of man today has reduced to the point that some of the villages in the valley can be defined as completely abandoned. Others remain manned only by a handful of inhabitants and then repopulated a little in the summer with a modest tourism consisting almost exclusively of the temporary return of the descendants of the ancient emigrants. Electricity, where it exists, has only been brought to the valley for a few years thanks to the helicopters that have lowered the pylons from above. The Boreca valley is in fact very steep and deep, with a very narrow “V” profile, not at all softened by glacial erosion of which no trace can be found. The main center – so to speak – is Zerba, which has dignity as a municipality, and is dominated by the remains of a castle.
Some archaeological finds testify to an ancient population of the area. There is also a fable of a stop by Hannibal’s army in Val Boreca after the famous battle of Trebbia against the Romans in 218 BC. Some toponyms (the same Zerba, Artana, Tartago) who want a Phoenician ancestry would attest. Historical evidence of the passage of Hannibal, however, there are none and it is not even certain that the leader, after the battle, to cross the Apennines climbed the Trebbia.
As mentioned above, the main value of the Boreca valley is its environmental heritage, with chestnut and tall beech trees and coppice woods also of chestnut and beech, as well as oak and hornbeam. There are also resinous forests of artificial plant (also common in the adjacent Avegnone valley) and large grasslands dominated by the peaks of Mount Lesima to the north (the highest peak of the whole Trebbia valley with its 1724 meters above sea level), Chiappo and Carmo to the west and Alfeo to the south, all reachable through paths that partly rise from the Piacenza side of Ottone and Zerba and partly originate from the Giovà pass, which represents the access to the Boreca valley from the Pavia side.
Faced with the economic collapse of the valley, witnessed by the numerous literally abandoned villages, real ghosts of a past that is not too far away, the only heritage that can be exploited remains nature and landscape, which in Val Boreca reach a quality so high that it is one of the most interesting centers of a hoped for future Park of the Val Trebbia here. How such a park can also become an opportunity for development is a difficult question that would lead us to complex reflections, to be extended to a large part of our mountain territory. But that in the future this development cannot be separated from the enhancement of the environment is an increasingly widespread sensation.

taken from: AN ISLAND AMONG THE MOUNTAINS - Fabrizio Capecchi - CROMA Editions - 1990

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This subject could have been dealt with in the part concerning the Val Trebbia; the Boreca stream is, in fact, its left tributary. But, for the singular link I have established with this place, I have reserved the last pages of this book for it. At the end of two years of patient work, I joyfully remember the valley that recorded my first encounter with this beautiful region. There the idea of ​​this work was born; there the passion that always accompanied me in the countless surveys, during which I collected the material now gathered here. The country of Pey has been my constant point of support. I had heard, for the first time, of the Boreca valley, from a friend from Asti, who went there to fish for trout. I had to resort to a detailed road atlas to locate it exactly. On that occasion I noticed the curious interweaving of valleys that gather around the watershed between the Trebbia and Scrivia, further delimited by the borders of four provinces belonging to four different regions. Certainly a singular situation. I decided on a site visit to personally verify the qualities and circumstances that had been described to me. Val Boreca, on paper, was the least marked by roads and villages, and the choice fell on that. Leaving the main road just before Ottone, I took the branch on the right. From that moment I felt a certain trepidation, which later accompanied me throughout the day; it happens when one enters an unknown place, where the fear of violating its secrets adds to the desire to discover its appearance. A sensation enhanced by the gloomy north face of Mount Alfeo, which looms over the road, which is very steep and covered by a thick beech forest. A little further on, on an offshoot of M. Alfeo, a small plateau among the trees houses the town of Tartago. At first I thought it was not possible to reach him by car; I had not noticed that the dirt road crosses the dry bed of the stream, to go up, with numerous hairpin bends, the opposite side. The lack of water at that point is due to the fact that, a little further upstream, under the inhabited area of ​​Zerba, the course of the Boreca is harnessed by a dam, from which the pipes that emerge in Val Trebbia, nearLosso, start where there is a small power plant. I went on to Cerreto, Zerba, Vesimo, along a road carved out of the rock, then without parapets. The stream had disappeared from view, and I had to stop the car and lean into the gorge, to see small white sections between the stones. Vesimo, it is said, is the country on which the sun always shines; even when (a strange phenomenon, also observed by me several times), the peaks around and other countries are shrouded in fog. From Vesimo you can enjoy a splendid glimpse of the upper part of the Boreca valley, in its last seven kilometers, where the course of the stream turns south, up to the slopes of Mount Carmo. From Vesimo starts the only road that crosses the Boreca, frequently threatened by falling rocks, along which you reach, on the opposite side, the town of Belnome. From the crown of mountains, steep ridges covered with woods come off, which intertwine with each other, forcing the stream to describe loops, to overcome rocky ravines, to form other waterfalls and blue pools of water, even several meters deep. A show that can only be observed by going up the stream. It is what I did that first time, alone, with a pinch of unconsciousness, which pushed me into an adventure that I would gladly try again, but in the company of a friend. I was encouraged by the passion I have always had, since I was a child, for places like these; and the memory of "undertakings" carried out elsewhere, with my father, when every year, as a destination for a day of fishing, we went back to the sources of a stream, in the Val di Vara. It was always exciting, after one last turn, to see the river disappear in two black holes in the rock, which sank into the heart of the mountain. But the Boreca springs were unattainable. The last section was a steep wall which the flow of water had made slimy and impractical. I left the gorge, climbing on the left in the beech forest. With difficulty, I reached the summit of Mount Carmo, from where I was able to admire, for the first time, the wonderful panorama of the valleys between the Trebbia and the Scrivia. From a distance I saw Vesimo, and the road that went down to the river where I had left the car. It was unthinkable to go down the stream; it was already past five in the afternoon, and the darkness would come earlier. I crossed the ridge for a while, until I found a path that went down halfway to cross two villages, which I had not been able to see from the bottom of the valley. At Bogli I asked for some indications to continue the journey. Several times, for the approach of the evening, because the forces began.