Polonnaruwa was the capital from the 11th to the 13th century. Its centerpiece is the Terrace of the Tooth Relic. Best examples of sculpture at Polonnaruwa are seen at Gal Vihara, a monument with four beautifully carved images of the Buddha. A sampling of Medieval Buddhist art is preserved at the Tivanka Image House. One of the island’s largest known irrigation reservoirs (5940 acre) is the Parakrama Samudraya, (Sea of Parakrama), an island sea constructed in the 11th century.