The West Tower battlements were located on the topmost floor of the West Tower at Hogwarts Castle. After rescuing Sirius Black from Filius Flitwick's office, Harry Potter and Hermione Granger left for the Hospital Wing via a door at the battlements. They descended one staircase onto a corridor, then two other staircases, and then were able to get to the hospital just before Albus Dumbledore magically sealed it.