Ostrava is the third largest city in the Czech Republic and the second largest urban agglomeration after Prague. Located close to the Polish border, it is also the administrative center of the Moravian-Silesian Region and of the Municipality with Extended Competence. Ostrava was candidate for the title of European Capital of Culture 2015. Ostrava is located at the confluence of the Ostravice, Oder, Lučina and Opava rivers. Its history and growth have been largely affected by exploitation and further use of the high quality black coal deposits discovered in the locality, giving the town a look of an industrial city and a nickname of the “steel heart of the republic” (Czech: ocelove srdce republiky) during the communist era of Czechoslovakia. Many of the heavy industry companies are being closed down or transformed, yet the city remains one of the most polluted in the EU