Mangdeok-saji is a temple site on the slopes of Nangsan in Baeban-dong, Gyeongju. It faces Sacheonwangsa, and its original construction is dated to the reigns of King Munmu or King Sinmun. Samguk Yusa records the background of building Sacheonwangsa to repel an invasion from Tang China. The story of the monk Seonyul, who died and returned to life, is also told there.