Ostrava ( , Ostrau, Ostrawa) is the third largest city in the Czech Republic, however it is the second largest urban agglomeration after Prague. It is also the administrative center of the Moravian-Silesian Region and of the Municipality with Extended Competence. Ostrava is located at the confluence of the Ostravice, Oder and Opava rivers. Its history and growth have been largely affected by exploitation and further usage 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” (ocelové srdce republiky) during the communist era of Czechoslovakia. Many of the heavy industry companies are being closed down or transformed nowadays.