Shiraz pronunciation is the sixth most populous city of Iran and the capital of Fars Province. In 2009 the population of the city was 1,455,073. Shiraz is located in the southwest of Iran on the Roodkhaneye Khoshk (Dry river) seasonal river. It has a moderate climate and has been a regional trade center for over a thousand years. It is regarded as one of the oldest provinces of ancient Persia. The earliest reference to the city, as Tirazi, is on Elamite clay tablets dated to 2000 BC. In the 13th century, Shiraz became a leading center of the arts and letters, due to the encouragement of its ruler and the presence of many Persian scholars and artists. It was the capital of the Persia during the Zand dynasty from 1750 until 1781, as well as briefly during the Saffarid period. Shiraz is known as the city of poets, literature, wine and flowers.