Located near Torno, on the east side of the western branch of Como Lake, the Plinian source attracted the scientific attention of many scholars, famous and even less-known, through the time. To explain the phenomenon they made many fieldwork experiment using different instrument and scientific models.

The peculiarity of this source, that, even today, flows from the Plinian Villa, built in 1570 by Count Anguissola as a refuge after his involvement in the Farnese Duke death, is its particular intermittent flow. It was found that the rate of the water flow change even several times a day. What is the cause of this singular irregularities?

This question was so interesting, from the hydrological, geological and physical aspects, that, even nowadays, it's the subject of many studies and analysis, as shown a recent work base on the scientific data collected from the ancient time.

The first who described this phenomenon were the two Plinii, the Old and the Young; after Kircher, Leonardo da Vinci, Ghezzi and many other scholars of the 18th and 19th century, have done field studies to give a plausible answer.

Several explanations have been given over the centuries and all of them were analyzed by Carlo Amoretti, a prolific ligurian polygraph and a ‘curious’ investigator of the nature, who lived between 18th and 19th century. Even if he was a less known scholar than many other of his time, Amoretti was able to spreading the interest on different fields of knowledge, observing and descibing many different scientific phenomena.

This was also the case of the Plinian source, where he went several times during his many trips to Como Lake in order to understand, on the field, this ‘mysterious’ phenomenon.

So, after considering the hypothesis proposed by predecessors and contemporaries, Amoretti was persuaded that the particular geological conformation of the mountains above the source, rich in caves and crevices, allowed the wind to enter inside, causing the irregularity of the flow. To test his idea, he made speleological explorations entering into some of the Vallassina's caves, in the mountains between the two branches of the Como Lake, such as the Gravinate cave. In one of this speleological trips Amoretti went with Alessandro Volta, famous italian physicist.

The study of Plinian source is, therefore, an example of how the fieldwork explorations, especially in the 18th and 19th century, have been a powerful tool for the geologic and nature knowledge of the landscape.