The East Towers, also referred to as the East Wing, are a section of Hogwarts Castle. The name “East Towers” is not explicitly mentioned in the seven original novels; however, the term “East Wing” is used once. This area of the castle is known primarily through supplementary materials, which place several important classrooms and locations within it. The only canonical reference to this part of the castle occurs when Dolores Umbridge, searching for a fugitive Albus Dumbledore, speculates that he might be hiding in “the East Wing,” suggesting it is a known, distinct section of the castle large or complex enough to offer concealment. According to the Pottermore website, the East Tower is the location of the History of Magic Classroom. This situates it as a part of the castle frequented by students from all years and Houses.
While the name “East Towers” is not used in the novels, its constituent parts play a role. The “East Wing” is mentioned by Dolores Umbridge during her takeover as Hogwarts High Inquisitor. Her suspicion that Dumbledore might be hiding there indicates that she, and likely others, view it as a sprawling or less-trafficked part of the castle suitable for a hideout. The most significant events connected to this area occur within the History of Magic Classroom. Students spend considerable time in this room throughout their education, where Professor Cuthbert Binns delivers his famously monotonous lectures. It is the setting for numerous scenes where Harry Potter, Ron Weasley, and Hermione Granger discuss important matters under the cover of the boring lessons, and it is where Harry often receives visions through his scar connection to Lord Voldemort.
The definitive naming of the “East Towers” and the placement of specific rooms within it largely stem from materials outside of the original seven novels.