Anapji Pond (or ‘Samguk-sagi’) is a man-made pond located at the Banwolseong Palace Complex in the coastal city of Gyeongju. It dates back to the Silla Dynasty (roughly 674 CE) and was commissioned by King Mumnu who was heavily influenced by Taoism.
While beautiful during the day, I would suggest sticking around until sunset. The entire complex is lit perfectly for night photography (a sturdy tripod is recommended). Not only the palace buildings, but also the surrounding forest and small river areas have multi-colored lighting.
For more information:
Life in Korea
Asian Historical Architecture