Ústí nad Labem is a city in the north-west of the Czech Republic, on the River Elbe. It is the most populous city in the North Bohemian Region. The city has about 100,000 inhabitants. Ústí is an important industrial center, with steelworks, coal mines, and chemical and glass factories. It is also an important railway junction. The city has a well-preserved historic center, with a number of churches and a castle.