Gliwice (German: Gleiwitz) is a city in Upper Silesia, southern Poland, near Katowice. Gliwice is the west district of the Upper Silesian Metropolitan Union – a metropolis with a population of 2 million. The city is located in the Silesian Highlands, on the Kłodnica river (a tributary of the Oder). Situated in the Silesian Voivodeship since its formation in 1999, Gliwice was previously in Katowice Voivodeship. Gliwice is one of the cities of a 2.7 million conurbation known as the Katowice urban area and is within the larger Silesian metropolitan area, which has a population of about 5,294,000 people. The population of the city is 185,196 (March 2014). Founded in the 13th century, Gliwice is one of the oldest settlements in Upper Silesia. Despite rapid development during the industrial and socialist eras, the central Old Town fully retained its medieval character and part of its defensive walls date back to the 15th century. Gliwice is primarily known as an industrial city with developed industries such as coal mining, steel making and production of machinery and chemicals. It is also an important educational centre, being home to most of the departments of the renowned Silesian University of Technology. The city's long history had a great impact on the architecture of its buildings and structures; the most characteristic feature of Gliwice is a 110-meter high radio mast, which is thought to be the world’s tallest wooden construction.