Complex sentence: In terms of both population and area Ostrava is the third largest city in the Czech Republic, the second largest city in Moravia, and the largest city in Czech Silesia; it straddles the border of the two historic provinces of Moravia and Silesia.
Split into simpler sentences: In terms of both population and area Ostrava is the third largest city in the Czech Republic, the second largest city in Moravia, and the largest city in Czech Silesia. It straddles the border of the two historic provinces of Moravia and Silesia.