Polonnaruwa Era existed between AC 1065- 1120. The governing period of this time was about 186 years and 19 rulers had sat on the throne in that period. During the final period in the Anuradhapura era, the cholas shifted the political power to Polonnaruwa, which was situated in the eastern side of the dry zone. The main reason was security, as it was regarded as a strategic location to guard against an invasion from Ruhuna, the refuge of the Sinhalese liberation force.
Polonnaruwa had its own fabulous Buddhist architecture and irrigational network that had been built over the centauries by earlier sinhala rulers. (Ex- Minneria Tanks)
The First Sinhalese king to rule in this period was King Wijayabahu who ruled for 55 years after he defeated the cholas.(AC 1065-1120). He restoered Buddhism to its former glory and was also responsible for economic regeneration.
The Next famous King to take over from Vijayabahu is KingParakramabahu (AC 1164-1197) He unified the country under one rule and built a remarkable series of irrigation work including the massive Parakrama Samudraya.
Nissanka Malla was also a king to take notice of, because he also stabilized Sri Lanka during his period. But his death brought instability & a pirate named Magha, who came from south India conquered Polonnaruwa & executed many years of ruthless control over the island.