Location from harry-potter-half-blood-prince by
The castle under shadow — security is tighter, Dumbledore is absent on mysterious errands, and Death Eaters invade through a Vanishing Cabinet.
Hogwarts security has been enhanced with Auror patrols, enhanced enchantments, and Filch checking every student with a Secrecy Sensor. But the protection is insufficient — Draco repairs the Vanishing Cabinet in the Room of Requirement, creating a passage that bypasses every defense. Death Eaters enter the castle. The school year ends with Dumbledore's body on the ground below the Astronomy Tower. White marble tomb by the lake. The future of the school uncertain.
The ancient castle, corridors patrolled by Aurors and protective enchantments. The Room of Requirement hides Draco's secret. The Astronomy Tower becomes the site of the greatest loss.
Also known as: Hogwarts, the castle