Hogwarts occurring is a passage to the Hog's Head bar that formed before the Battle of Hogwarts. Due to the nature of the Room of Requirement, it is possible that several passages to different locations could be accessed from the Room. The three passages out of Hogwarts that Filch does "not" know about are: A further link between two vanishing cabinets, one in the school and the other in Borgin and Burkes in Knockturn Alley presumably worked until "Chamber of Secrets" when Peeves (persuaded by Nearly Headless Nick) smashed the Hogwarts cabinet. The passage was reopened in "Half-Blood Prince" when Draco
Hogwarts "Half-Blood Prince" Harry used the Room of Hidden Things to stash his copy of "Advanced Potion-Making", describing it as the size of a large cathedral and packed to overflowing with items hidden by Hogwarts inhabitants over the years, such as old potions, clothing, ruined furniture, an old tiara (which happened to be one of Voldemort's Horcruxes), or books which were "no doubt banned or graffitied or stolen." He later realised that Draco had been using the room in that state to hide and repair the Vanishing Cabinet to use it to smuggle Death Eaters into Hogwarts. Ironically, while Harry tries