The Room Of Requierments placed at Hogwarts Castle, and knowes as the room which comes and goes.
This is where Harry teaching Dumbledore's Army (D.A.) spells and curses that are very usefull at wizard duling.
Dumbledore's Army practiced in 1996-1998 duling agenst the death eaters and Lord Voldemort (knowes as You-Know-Who, the dark lord and the man who must not be named). The room of requirements is ariving in "Harry Potter and The Order Of The Phoenix" (movie been realised in July 2007, and rated in U.S.A. PG-13, and in Australia M). Dumbledore's Army joined The Order Of The Phoenix.
To come in, you need to go 3 times near the secret door, and think about the thing that is needed. A few seconds later, the door will apear. #Floo_Butter #Harry_Potter #Hogwarts