Sa Song Hong is a historically significant ancient reservoir located west of the Chan Royal Palace walls in Phitsanulok. The reservoir is rectangular, measuring approximately 40 meters in width and 160 meters in length, aligned on a north-south axis. It is divided into two sections by a central earthen partition, giving it the name "Sa Song Hong" (Two-Chambered Pond). Believed to have been constructed for irrigation within the palace grounds during the early Ayutthaya period (15th-17th centuries), it has served as a source of sacred water for royal ceremonies from ancient times to the present day.