The Volga River is the longest river in Europe, stretching over 2,300 miles through western Russia. It runs through or borders 11 of Russia's 20 largest cities, making it an important transportation route and tourist attraction. However, the river also receives large amounts of industrial waste from factories along its banks, polluting the waters. Two products from the Volga region are black caviar from sturgeon fish and the fish themselves, though sturgeon is known to taste unpleasant despite the high market value of its roe. Bridges span the wide Volga frequently, though the total number is difficult to determine.