The Kilwa Sultanate was a medieval sultanate centred at Kilwa, in modern-day Tanzania. At its height, its authority stretched over the entire length of the Swahili Coast, including Kenya. It was said to be founded in the 10th century by Ali ibn al-Hassan Shirazi, a Persian Sultan from Shiraz in southern Iran. However, scholars have suggested that claims of Arab or Persian origin of city-states were attempts by the Swahili to legitimise themselves both locally and internationally. Since the 10th century, rulers of Kilwa would go on to build elaborate coral mosques and introduce copper coinage.