The King's Study is a location from The Legend of Zelda: Breath of the Wild. It is the former private study of King Rhoam Bosphoramus Hyrule hidden behind a metal bookcase in the Library inside the Hyrule Castle in the Hyrule Field region of Central Hyrule.
Before the Great Calamity, King Rhoam used this room as his private study where he wrote his thoughts in his private journal. After the Great Calamity, the room remained hidden thanks to the metal bookcase concealing it. The room and journal survived the Calamity intact. Link can use the Magnesis Rune to move the bookcase to enter the concealed room. A Royal Guard's Shield also spawns within the study.