In between the provinces of Bergamo, Milan, Cremona, Mantua and Lodi, exactly in the area extending for about 60 kms from Cassano d’Adda to Cremona, in the Middle Ages existed a lake called Gerundo (from the Lombardy dialect: gèra, gerù, gerùn, meaning “gravel”); in its centre was the island Fulcheria (another Longobard placename) , corresponding to the city of Crema. The lake extended on a vast territory from Brembate to Pizzighettone, touching Lodi on the Western shore, where today the river Adda flows, and Fara Olivana and Grumello Cremonese on the Eastern side; it covered part of the valleys of rivers Chiese and Oglio, almost reaching the point where they merge in the Po river. Specifically, wide areas delimited by an escarpment indicate the ancient lakebed, or, better, its deepest point; such marking can be clearly detected on the western shore of Adda. Its disappearance is due to the drainage work carried out by the monks and the strengthening works made on the Muzza channel by the people of Lodi, and also to geologic factors of drainage and settlement, such as the leverage of moraine sediments where the Adda river merges into the Po. Evidences such as dugout canoes found in the riverbeds crossing this area, prove that the Gerundo lake existed and could be sailed. One of the most beautiful and well conserved exemplars of dugout can be seen in the court yard of the Museum of Crema, restored with special substances which stopped the dissolution process. Columns for the docking of the boats were also found in Arzago d'Adda, Pandino, Rivolta d'Adda, Casirate d'Adda, Truccazzano, and some more place names (Brignano Gera d'Adda, Fara Gera d'Adda, Misano di Gera d'Adda etc.) are also a proof of the existence of the lake.
According to popular folklore, the Gerundo lake was inhabited by a dragon called Tarànto or more commonly Tarantasio, a repugnant and poisonous snake, pestering the air with its noxious breath that caused the death of many. Every popular legend is always based upon real facts, and certainly the marshy waters were a hotbed for malaria and other swamp diseases. The father of the legendary beast, according to the myth, was Ezzelino da Romano, imperial vicar and son-in-law of Federico III, landlord of a territory including most of Veneto and Brescia. He was such a cruel commander that the Pope Innocenzo IV excommunicated him and in 1254 indicted a crusade against him, led by Azzo VII d'Este. In Cassano d'Adda, in 1259, Ezzelino was defeated and wounded to death. According to tradition, he was buried in Soncino. His grave was the cradle of Tarantasio, malign reincarnation of the wicked lord. More “scientific” evidence, in the form of gigantic bones preserved in some churches of the territory, were found in the ancient lakebed. A gigantic bone, specifically a rib of the dragon, can still be seen hanging from the ceiling of the sacristy in the Church of San Bassiano in Pizzighettone. The rib probably belonged to a prehistoric whale or pachyderm. Yet Taranta, a fraction of Cassano d’Adda, was named after the mythological monster, so as the several “Vie della Biscia” (which might be translated as “Serpent Tracks”) located in the countries that once were on the lake shores (although many of these streets have changed names in the modern toponymy). But still a more concrete proof can be found in Calvenzano, where a three-meter wall was built to defend people from the attacks of the dragon. Several legends regarding the monster have their fil rouge in the coincidence between the killing of Tarànto and the drying up of the lake. Popular sources connect the drainage and reclamation of the lake, as well as the killing of the creature, either to Saint Christopher or to Federico Barbarossa. The latter hypothesis is the most suggestive, as the forefather of the noble Visconti dynasty would have later embellished his family’s emblem with the symbol of the defeated monster.
Few know that Tarantasio is also an international celebrity, as it was the original inspiration for Eni’s well-known six-paws dog that represented Agip. The first natural gas vein ever was discovered in 1944 in Caviaga, a fraction of Cavenago d'Adda, province of Lodi, thus in the ancient lacustrine territory of Gerundo . The dragon’s pestilential breath also has a scientific explanation: it was due to the presence of natural gases flowing from the underground, formed by soaked layers of alluvial sediments. Right here in 1952 AGIP found some huge veins of natural gas and ENI invented the symbol which is now famous all over the world, inspired by our legendary monster Tarantasio.