Sri Lanka, Polonnaruwa (ancient city). Vatadage moonstone. Polonnurawa is 216 km from Colombo. It was the capital of Sri Lanka in medieval times. Used by the Sri Lankan kings as a 'country residence' from the 7th century, Polonnurawa became Sri Lanka's capital in the 11th century AD. The Chola empire came to power in the late 9th century and lasted until around the late 13th century. For about seventy-five years, Sri Lanka was ruled as a Chola province and it was during this time that the practice of Buddhism became surpassed by Hinduism. The Chola empire chose Polonnaruwa to be their capital as a result of its location near the Mahaweli Ganga, a river that formed a natural barrier to potential Sinhalese attacks from the South.