Katowice is the capital of the Silesian Voivodeship, and one of the largest cities in southern Poland, boasting a metropolitan area of over 2.7 million inhabitants. It is one of the richest cities in Poland and one of the most economically powerful cities in the European Union, with output that surpasses the $100 billion mark annually. Its importance as a business hub also makes it a popular city to host trade fairs; the UFO-shaped conference center called Spodek was for many years the largest indoor arena in Poland. Katowice was one of the epicenters of the Industrial Revolution in Poland, and the growth the city experienced allowed it to diversify and build a reputation as not just a hub of trade but also transportation, culture, and science. Katowice is a UNESCO City of Music and is where the Polish National Radio Symphony and Orchestra is based.