Sap Biosphere Reserve is a unique ecological phenomenon surrounding the Tonle Sap. It encompasses the lake and nine provinces: Kampong Thom , Siem Reap , Battambang , Pursat , Kampong Chhnang , Banteay Meanchey , Krong Pailin , Otdar Meanchey and Preah Vihear . In 1997, it was successfully nominated as