modelled after their ruler. While gold coins also existed within the kingdom and were used, they largely disappeared in the very last days of Parakramabahu I. This may have been due to an economic crisis caused by the burden. It is to be noted that the coinage of Polonnaruwa shows a great resemblance to that of RajaRaja I of the Chola kingdom. The Setu coins found in South India are also likely from the kingdom of Polonnaruwa, as the Chola or Pandya kingdoms had no reason to use these. Trade with the Chinese dynasties was extensively high at the period, and coins belonging to the Song dynasty have been found throughout Polonnaruwa. Meanwhile, in its colonial territories in South India, the Kahapana currency was used. Technology and structures The ancient Sinhalese civilization was technologically advanced. The irrigation technology of Polonnaruwa was much similar to the Anuradhapura period ones but was even more advanced. James Emerson Tennent writes: Divine architecture ranging from larger dams to artificial seas, such as the Parakrama Samudra, always required advanced technology and were built in unique ways. Vatedage The Vatadages were built since the Anuradhapura period, however, the peak was reached during the Polonnaruwa period. The Polonnaruwa Vatadage is considered the "ultimate creation" out of all Vatadages. A Vatedage is built for the protection of a small stupa. The structure has two stone platforms decorated with elaborate stone carvings. The lower platform is entered through a single entrance facing the north, while the second platform can be accessed through four doorways facing the four cardinal points. The upper platform, surrounded by a brick wall, contains the stupa. Four Buddha statues are seated around it, each facing one of the entrances. Three concentric rows of stone columns had also been positioned here, presumably to support a wooden roof. The entire structure is decorated with stone carvings. Some of the carvings at the Polonnaruwa Vatadage, such as its sandakada pahanas, are considered to be the best examples of such architectural features. Although some archaeologists have suggested that it also had a wooden roof, this theory is disputed by others. Nissanka Malla reign The Hatedage and Nissanka Latha Mandapaya were built by Nissanka Malla (1187-1197) to store the relics. Several relics including relics of the Tooth of Buddha and Rice Bowls used by the Buddha are said to have been held in the Hatadage. Several historical sources including the