Instruct: Given a question, retrieve passages that can help answer the question.
Query: How long is the Po river in Italy?
The Po (/poʊ/, Italian:[ˈpɔ]; Latin: Padus or Ēridanus; Ancient Greek: Πάδος, romanized:Pádos or Ἠριδανός, Ēridanós; Ancient Ligurian: Bodincus or Bodencus) is a river that flows eastward across northern Italy. The Po flows either 652km (405mi) or 682km (424mi) – considering the length of the Maira, a right bank tributary. The headwaters of the Po are a spring seeping from a stony hillside at Pian del Re, a flat place at the head of the Val Po under the northwest face of Monviso (in the Cottian Alps). The Po ends at a delta projecting into the Adriatic Sea near Venice. It has a drainage area of 74,000km² in all, 70,000 in Italy, of which 41,000 is in montane environments and 29,000 on the plain.[2] The Po is the longest river in Italy; at its widest point its width is 503m (1,650ft).[1] The Po extends along the 45th parallel north.
Beluga sturgeon abounded in the Po River in the 16th century and they were a frequent capture. The first known reference to the preparation of sturgeon caviar in Italy is in Messisbugo's books. He described how to prepare the caviar both to be consumed fresh and to be preserved.
Malone is a long stream () of the Metropolitan City of Turin in Piedmont, north-western Italy. It is a left side tributary of the river Po which flows through the Canavese.
The Cimbri had penetrated through the Alps into northern Italy. The consul Quintus Lutatius Catulus had not dared to fortify the passes, but instead he had retreated behind the river Po, and so the land was open to the invaders. The Cimbri did not hurry, and the victors of Aquae Sextiae had the time to arrive with reinforcements. At the Battle of Vercellae, at the confluence of the river Sesia with the Po, in 101 BC, the long voyage of the Cimbri also came to an end.
Piedmont is the second largest of the 20 administrative regions of Italy, after Sicily. It is broadly contiguous with the upper part of the drainage basin of the river Po which rises from the slopes of Monviso in the west of the region and is Italy’s largest river. The Po collects all the waters provided within the semicircle of mountains (Alps and Apennines) which surround the region on three sides. 
The Tanaro (), known as Tanarus in ancient times and "Tane" or "Tani" in piedmontese language, is a long river in northwestern Italy. The river begins in the Ligurian Alps, near the border with France, and is the most significant right-side tributary to the Po in terms of length, size of drainage basin (partly Alpine, partly Apennine), and discharge.
The Versa is a tributary of the Po River which runs through the Province of Pavia in northern Italy.
The coldest month is January: the Po valley's mean temperature is between −1–1 °C. Winter morning lows can occasionally reach −30 to −20 °C in the Alps and −14 to −8 °C in the Po valley. Summer is usually more stable with July temperatures are 22–24 °C north of river Po, like in Milan or Venice, and south of river Po can reach 24–25 °C like in Bologna.
The vast valley around the Po is called the Po Basin or Po Valley (Italian Pianura Padana or Val Padana); in time it became the main industrial area of the country. In 2002, more than 16 million people lived there, at the time nearly ⅓ of the population of Italy.[1]
The Venetian Plain, or Venetian-Friulan Plain ( or ) is a major geographical feature of Italy. It extends approximately from the River Adige to the River Isonzo, in a southwest-to-northeast direction, including almost all the flatlands of Veneto and Friuli. It is not properly related to the Po River basin, but it is often considered as part of the Po Valley since the flatlands of Veneto and Friuli do not drain into the Po, but they effectively combine into an unbroken plain. Sometimes, instead of the River Adige, the Euganei Hills and Berici Hills are considered to be its western border.
Stura di Demonte () is a long river in northwestern Italy (Piedmont). 
The river is a tributary to the river Tanaro, which is a tributary of the river Po. Its source is in the Alps, near the border with France. It flows through Demonte and Cuneo before joining the Tanaro just east of Cherasco.
Scardinius hesperidicus is a species of ray-finned fish in the family Cyprinidae.
It is native to Po and Adriatic drainages east of the Po in Italy, San Marino, and Switzerland, and has been introduced into other area watersheds, especially in Italy. Its natural habitats are rivers and freshwater lakes.
The Po Valley, Po Plain, Plain of the Po, or Padan Plain ( , or "Val Padana") is a major geographical feature of Northern Italy. It extends approximately in an east-west direction, with an area of including its Venetic extension not actually related to the Po river basin; it runs from the Western Alps to the Adriatic Sea. The flatlands of Veneto and Friuli are often considered apart since they do not drain into the Po, but they effectively combine into an unbroken plain.
The Adda (Latin "Abdua", or "Addua"; in Lombard "Ada" or, again, "Adda" in local dialects where the double consonants are marked) is a river in North Italy, a tributary of the Po. It rises in the Alps near the border with Switzerland and flows through Lake Como. The Adda joins the Po a few kilometres upstream of Cremona. It is long. The highest point of the drainage basin is the summit of la Spedla (a subpeak of Piz Bernina), at .
The Province of Pavia is in the region of Lombardy in northwestern Italy. It is bounded to the north by the provinces of Milan and the Lodi, to the southeast by the Province of Piacenza (Emilia-Romagna), and to the southwest it is bounded by the Province of Alessandria (Piedmont). The province is crossed by the rivers Ticino and Po, which meet four kilometres south of the capital, Pavia. The province contains 190 communes and the River Po is navigable up to its confluence with the Ticino. There are three regions of the province, the Pavese, which is entirely in the Po Valley, the Lomellina, which is also completely in the Po Valley but between the Ticino and the Po, and Oltrepò, to the south of the Po and which includes Monte Lesima (1,724 m (5,656 ft)), a mountain in the Apennine Mountains which is the highest point in the province. The territory of Siccomario, at the confluence of the two great rivers, should properly be included in Lomellina, but for historical reasons it is considered part of Pavese. Another large river flowing through the province is the Olona.
The Reno () is a river of Emilia-Romagna, northern Italy. It is the tenth longest river in Italy (the sixth longest of those that flow directly into the sea) and the most important of the region apart from the Po. 
Cristoforo da Messisbugo in his book "Libro novo nel qual si insegna a far d'ogni sorte di vivanda", Venice, 1564, at page 110, gave the first recorded recipe in Italy about extraction of the eggs from the roe and caviar preparation "to be consumed fresh or to preserve".
The writer and voyager Jérôme Lalande in his book ""Voyage en Italie"", Paris, 1771, vol. 8 page 269, noted that many sturgeon were caught in the Po delta area in the territory of Ferrara.
In 1753 a diplomatic war broke out between the Papal States, governing the Ferrara territory, and the Venetian Republic about sturgeon fishing rights in the Po river, the border between the two states. From about 1920 and until 1942 there was a shop in Ferrara, named "Nuta" from the nickname of the owner Benvenuta Ascoli, that processed all the sturgeons caught in the Po river for caviar extraction, using an elaboration of the original Messisbugo recipe, and shipped it to Italy and Europe. Production was sporadically continued by a new owner until 1972, when sturgeon stopped swimming up the Po river. Since 2015, some sturgeon have reappeared in the Po.
Currently, Italian caviar is obtained almost entirely from bred sturgeons. The caviar production is concentrated predominantly in Brescia, which is considered the capital of Italian caviar: in this area, in Calvisano, is located the world's largest sturgeons farm that produces annually 25 tonnes of caviar. Italian caviar is generally the most sold and appreciated in the world: Italy is the world's first producer.
Tartaro-Canalbianco-Po di Levante (Latin: Tartarus) is a river of north-east Italy. It is the only river whose course runs between the Adige river and the Po river and flows into the Adriatic Sea.
Piedmont is the second largest of Italy's 20 regions, after Sicily. It is broadly coincident with the upper part of the drainage basin of the river Po, which rises from the slopes of Monviso in the west of the region and is Italy's largest river. The Po collects all the waters provided within the semicircle of mountains (Alps and Apennines) which surround the region on three sides.
The river flows through many important Italian cities, including Turin (Torino), Piacenza and Ferrara. It is connected to Milan through a net of channels called navigli, which Leonardo da Vinci helped design. Near the end of its course, it creates a wide delta (with hundreds of small channels and five main ones, called Po di Maestra, Po della Pila, Po delle Tolle, Po di Gnocca and Po di Goro) at the southern part of which is Comacchio, an area famous for eels. The Po valley was the territory of the Roman Cisalpine Gaul, divided into Cispadane Gaul (South of the Po) and Transpadane Gaul (North of the Po). The Po begins in the Alps, and is in Italy, and flows eastward.
Northern Italy is made of the basin of the River Po, which comprises the whole of the broad plain extending from the foot of the Apennines to that of the Alps, together with the valleys and slopes on both sides of it, the Venetian Plain and the Ligurian coast.
Northern Italy has the Alps as northern and western boundary and the Apennine Mountains as the southern one. In between the two mountain ranges lies a large plain made of the Venetian Plain and the valley of the Po, the largest river in Italy, which flows 652 km eastward from the Cottian Alps to the Adriatic Sea and receives all the waters that flow from the Apennines northwards, and all those that descend from the Alps towards the south. The Po Valley is the largest plain in Italy and held the vast majority of North Italian population.
Stura di Lanzo () is a long river in north-western Italy (Piedmont), in the Metropolitan City of Turin. It is formed from several tributaries near Lanzo Torinese. It flows into the river Po in Turin.
The Taro (Latin "Tarus") is a river in Emilia-Romagna, in northern Italy. It is a tributary of the Po and is long. It flows almost entirely in the province of Parma, west of the city Parma. The Taro flows into the Po near Gramignazzo, a frazione of the comune of Sissa, north of Parma.
Dora Baltea () or Doire Baltée () ( or "Duria Bautica"; (Valdôtain); , ), is a river in northern Italy. It is a left-hand tributary of the Po River and is about long.
Almost 40% of the Italian territory is mountainous, with the Alps as the northern boundary and the Apennine Mountains forming the backbone of the peninsula and extending for . In between the two lies a large plain in the valley of the Po, the largest river in Italy, which flows eastward from the Cottian Alps to the Adriatic. The Po Valley is the largest plain in Italy, with , and it represents over 70% of the total plain area in the country.