Katowice is a city in Silesia in southern Poland, on the Kłodnica and Rawa rivers (tributaries of the Oder and the Vistula respectively). It is a center of science, culture, industry, business, trade, and transportation in Upper Silesia and southern Poland, and the main city in the Upper Silesian Industrial Region. Today, Katowice is a rapidly growing city and emerging metropolis. It is the 16th most economically powerful city by GDP in the European Union with an output amounting to $114.5 billion. One of the hidden gems of Poland, Katowice especially delights the senses in April with its numerous flowering lilac trees.