The Sassanid Empire was a major Persian state that existed from 224 to 651 CE. It was founded by Ardashir I after defeating the last ruler of the Parthian Empire. The Sassanids are known for their achievements in art, architecture, and governance, as well as their conflicts with the Roman Empire and later the Byzantine Empire. The empire's capital was Ctesiphon, located near modern-day Baghdad, Iraq. The Sassanids promoted Zoroastrianism as the state religion and made significant contributions to culture and science. The empire ultimately fell to the Arab Muslim conquests, leading to the spread of Islam in the region.