Trasimeno Lake had a tectonic origin.
3 million years ago, there was a shallow sea in this part of Umbria. Then a depression formed by geologic fractures, allowed the birth of Lake Trasimeno.
Historically, Trasimeno was known as The Lake of Perugia and this name makes it easy to understand the importance that the lake has always had for the whole of north-western Umbria and for the Tuscan Chiana district. In prehistoric times, this lake was extended so as to almost reach Perugia. Trasimeno is a mythological figure, joined with Agilla, a nymph born in Agello, now a hill midway between Perugia and Trasimeno, formerly an island in the lake. The Battle of Lake Trasimeno, took place on the north shore of the lake in April 217 B.C.E. during the Second Punic War. It's still debated where exactly where it happened, because the lake extended further and deeper at that time, so it could had been fought between Cortona and Tuoro. Near Cortona, there is a place called 'Ossaia', perhaps in memory of the bones found after that battle. Many legends were told about this battle, as the golden chariot of Flaminio, sunk in the middle of the lake.
The first civilization to inhabit this place was the Etruscans, and it's said that they found Trasimeno similar in shape to a liver. The Etruscan presence is not surprising, because when the lake was bigger, Perugia, Chiusi and Cortona, three of the main Etruscan cities, were all within 20km of the lake. Practically nothing remains from the Etruscan period, and only some traces of the Romans are found. Castiglione del Lago, has some Roman ruins and its main streets are structured like a chessboard in the Roman style.
Trasimeno is surrounded for half of its shores by hills, rich in olives that are among the most important resources of the local agriculture. On the western shore, near Tuscany, there are vineyards, and fruit and vegetables are grown. There, the hills are much lower and the climate is warmer. It's possible to see Monte Subasio near Assisi, about 70 km to the east, and Monte Amiata, about 70km to the west.
The vegetation includes pines, willows and poplars all around the shores, many over 30m tall.
The main towns, all quite small, are Passignano sul Trasimeno, Tuoro, Monte del Lago, Torricella, S.Feliciano, S.Arcangelo, Castiglione del Lago and Borghetto. Castiglione del Lago has the longest shore, because its on a the only significant peninsula of the lake. There were stories that this was an island that was joined to the shore by the Romans.
All around the lake there are old small towns, and isolated castles, like Zocco castle, now in ruins, and a tower near Passignano. Monte del Lago was originally built to control the road from Trasimeno to Perugia.
One of the features of Trasimeno lake is the local airport, the Eleuteri near Castiglione del Lago, once one of the main aviation schools in Italy, with elegant buildings, destroyed by retreating Germans in the summer of 1944.
Once this airport was almost as big as Castiglione. The mild climate and perfect visibility still allow the use of this airport for air meetings, even if the structures were left in ruins 60 years ago. There is a social center in this former airport, also crossed by one of the most important water courses, the Paganico torrent, that separated airport from the town.
Even before this airport there was an hydroscale in Castiglione del Lago. On the opposite shore, in Passignano, around 10km away, there was also an historic Italian airplane factory, the SAI Ambrosini, now abandoned as an industrial center, but still used as asocial center. It was founded around 80 years ago and the buildings still exist near the Passignano railway station. This company made several types of aircraft, designed by eng. Sergio Stefanutti.
Aircraft were tested at Eleuteri airport, only few kilometers away from this factory. SAI was involved mainly with Macchi during World War II. Eleuteri was also used as test center for the Ambrosini SS.4, advanced canard aircraft, which crashed in the second flight and the project was abandoned.
Trasimeno is relatively far from every major Italian city, the nearest of which is Perugia. There was an historic railway built over 100 years ago, with the main rail station in Terontola. Smaller railway stations are in Passignano and Castiglione del Lago.
Because of increased traffic, about 30 years ago a highway was built over the Passignano's road to Perugia. This highway passes near the north and the east shores of Trasimeno and goes to Perugia and Assisi. Many smaller roads, such as the statal 75, are also present, especially on the western side of the lake. The A1 Autostrada passes five km to the west of the Lake.
There are ferry boats, 3 small, 2 medium and two big (two decks) called Perusia and Agilla II, based in Passignano Port, also two dredges. There are ports in Castiglione del Lago (recently totally rebuilt), S. Arcangelo, S. Feliciano, Tuoro and several minor anchorages.
There are three islands in the lake. The second largest, Isola Maggiore, is the only inhabited one. The small fishing village, which reached its height in the 14th century, today has only around thirty residents. Most of the buildings, including the ruins of a Franciscan monastery, date from the 1300s. The largest of these isles is Isola Polvese, almost 1 km².
Maggiore is a 'hill', while Polvese is a more complex structure with planes and hills (Minore is a sort of sloped table). It is now uninhabited, but in the past there was a village with over 500 residents. Many centuries ago, there was a castle with a pentagonal structure near the shore, and a Olivetan monastery. The castle still remains and the ruins of the church and the monastery almost totally preserved, despite thie abandonment in the 17th century, due to bad climate and malaria. The malaria was finally eradicated only in the 1950s. There were other problems as well, since Trasimeno was fought over by Chiusi, Panicale, Perugia and Florence.
Florentine troops demolished Polvese in the 17th century, which started its decline, until by the 19th century there was only a caretaker. Of the many houses, nothing remains. Minore Isle, near Maggiore, is now uninhabited, totally covered by local vegetation except a little anchorage. In ancient times, there was a separation between the two communities, because Polvese was far away from Maggiore-Minore. It is said that the two communities fought against each other. But the real problems were from the regional 'powers' that fought over this lake for centuries.
The fishing in the lake used a particular technique called 'Toro', a very complex system that consisted of a wooden trap in the water and a circular structure to hold the net around it. The nets trapped the fishs and they were brought to the village to be dried. This system worked with a high water level, but was abandoned when the level dropped. A mock up of this system was built several years ago near Polvese Isle's port.
Trasimeno was always quite shallow, muddy, rich in fish (pike, carp, tench), but the shallow waters meant also malarial mosquitoes prospered.
To fight this problem, some small fish that voraciously ate mosquito larvae were imported from USA during the 1950s. These fish are widely scattered even in the lakes near Trasimeno. But despite billions of larvae eaten, there are still many mosquitoes and other insects.
Trasimeno water quality is still very good, as a misuration of Italia Nostra showed in 2005. The lack of big farms and a small population means a low pollution level.
In its history Trasimeno has known many crises. This lake is only 4 meters deep on average. Draining it was proposed to solve the problems of malaria and depth changes, but luckily they were rejected. At the end of the 19th century, the level changes were solved by building a channel near San Feliciano. This also lessened the malaria problem.
In 1929, there was a really cold winter, that totally froze the surface, so even cars could be driven over the ice. It was said that a car, by mistake (because the snow), reached Maggiore Isle. Also in 1957, there was another cold winter, so that Trasimeno's surface froze and there was heavy damages to the olive trees nearby. In 1985 another very cold winter froze Trasimeno and the olives as well for over 20 days. A less severe freeze happened in 1991. In 2002, the lake froze again, during very cold and dry winter. Finally, a strong easterly broke up the ice after 30 days. This is quite rare, given the latitude of this lake.
The Trasimeno climate is quite warm, with moderate winters. Summers can be very warm and humid, but in general the lake moderates the climate both in cold and warm conditions because even swallow water gives a moderate thermic inertia. From May to September, the temperature is warm enough to allow swimming.
Trasimeno has quite high hills (and the Pennines) to the east. These help to capture rain and partially protect the lake from cold eastern winds. It's likely that most of the water that goes to the lake comes from the wide web of streams from the western side of the lake.
The real problem of Trasimeno is the water scarcity. After World War II, its shores retreated a kilometer in the western sector (the eastern shore has a deeper and more steeply sloped bottoms). At the start of the 1970s, the shore retreated almost as much. After a period of abundance, from 1990, the lake had a disturbing and quite low water level. In 2003, the shore retreated over 100 meters and the level fell 128 cm. The main reason is lack of rain. From 2004 to the summer of 2006, there was plenty of rain (over 150 mm in the last 20 days of August 2005 alone, with over 700 mm to the end of year), but the fall and winter of 2006 have been almost totally dry, with a relatively hot climate. All Italy had this problem, and only in spring has there been significant rain, but still not neough. Despite this, the abundance of water that flowed into Trasimeno in the last 3 years has saved the lake from heavier problems. A new canal is under construction to bring water to the lake.
Human activity is involved in this problem. It was calculated that maize cultivation alone was equivalent to 5cm of water level per year, 1% of the overall evel. The large growth of the towns in the last 5 to 6 years all obviously require more water. There are ponds all over for agricultural use, many quite large, an additional problem for water resources.
Trasimeno is a great natural resource that should be rigorously protected and promoted. The inhabitants of the communes around Trasimeno and the Umbrian people have been successful in safeguarding their lake, whose waters are fit for swimming and whose valleys and islands are intact environments, providing a mirror of the past and a theme for a present suited to discovering a new means for man to interrelate with his habitat.
To better preserve it, in 1995 a natural park was established over all the surface and the shores. A 50 km bicycle path was opened in 2003 around the lake that allows tourists to explore it. There are also cross country paths, especially over the hills on the eastern side.
There are many castles all around Trasimeno. Many of them are in the center of small towns while others are isolated and in ruins. Castiglione del Lago, Passignano, Magione, Maggiore and Polvese isles have all a castle, while Zocco Castle, Montali Castle and others are on hilltops.
The Guglielmi Castle in Maggiore Isle is not ancient, as it was built in the late 1800s on the foundation of an old Franciscan church, and for many years was a well frequented place in the Trasimeno area. Lying in ruins during the last decades, until 1998 it was still visitable, then it was closed because the structure became dangerous. Now it is being restored by a new proprietor, but the work is far from completed.
Between Monte del Lago and S.Feliciano there is the old Zocco castle, ruined for decades. It is privately owned, but sadly nobody tends to its maintenance. This is one of the biggest castles of the area and the only one that, inside its sandstone walls, has a still untouched medieval keep. Some years ago it was probably inhabited, as there is a building fitted with an TV antenna, but now its only entry is closed.
The best preserved part is the eastern and the southern walls (here illustrated) one, while the rest of the walls are mostly demolished or fallen down. One of the southern towers has two enormous cracks with the middle.
Vernazzano pending tower (around 20 m height) is perhaps even more sloped than the famous Pisa's one. This unic remains of an ancient castle was built before 1089, when the whole castle was donated by Marchiones family to a monastery of Città di Castello. In 1202 began under control of Perugia and so this city gained the control of Northern Trasimeno. It was built on M.te Castiglione, near two turrents. The castle and the small city all around, called Vernazzano, were damaged by wars in 1400's and two century lather, by a strong heartquake (fullowed by others with the time). The erosions made by turrents caused the inclination of the tower in XVIII century. Vernazzano was rebuilt in the valley, away from this place, effective for the territory control, but not well suited to live in. So the Pending Tower is abandoned by almost 300 years. To avoid her breakdown, a steel armour was recently added, with plates and wires even thicker than 2-3 cm. The Tower, not well known as she is away from main streets (is visible from away, but with no immediate links to reach her), can continue to exist after 1000 years from her building.Trasimeno had a tectonic origin. 3 million years ago, there was a shallow sea in this part of Umbria. Then a depression formed by geologic fractures, allowed the birth of Lake Trasimeno.