The Ravenclaw Tower is located on the west side of Hogwarts Castle. Its entrance is found at the top of a tall, winding staircase. The door is a smooth, seamless expanse of ancient wood with no doorknob or keyhole, featuring only a bronze knocker in the shape of an eagle. Unlike the other Hogwarts house entrances, which require a password, entry to the Ravenclaw Tower is granted by correctly answering a philosophical question or riddle posed by the eagle knocker. This security measure reflects the wit and wisdom prized by Ravenclaw House, as anyone with sufficient intellect can gain entry, regardless of their house affiliation. A wrong answer will leave the individual waiting for someone else to come along and solve the next riddle. The Ravenclaw Common Room is a wide, airy, circular room with graceful arched windows that provide breathtaking views of the castle grounds, including the lake, the Forbidden Forest, the Quidditch pitch, and the herbology gardens. The decor is dominated by the house colors of blue and bronze, seen in silk wall hangings. The room is filled with tables, chairs, and bookcases, fostering an atmosphere of quiet study and intellectual pursuit. The ceiling is a magnificent dome painted with stars, which are echoed in the deep blue carpet on the floor. A notable feature of the common room is a tall statue made of white marble depicting the house founder, Rowena Ravenclaw. The statue shows her wearing her famous Diadem of Ravenclaw. Leading off from the main room are two doors, each leading to a spiral staircase: one to the boys' dormitories and the other to the girls' dormitories. The tower was presumably created along with the rest of the castle by its founders, with its unique features designed by Rowena Ravenclaw herself.
While mentioned throughout the series, the Ravenclaw Tower plays its most significant role in Harry Potter and the Deathly Hallows. During the Battle of Hogwarts, Harry Potter realizes that one of Lord Voldemort's Horcruxes is the lost Diadem of Ravenclaw and deduces it is likely hidden somewhere in Hogwarts. Believing it may be in the Ravenclaw Common Room, Harry is led to the entrance by Luna Lovegood. To gain entry, Harry must answer the eagle knocker's riddle: “Which came first, the phoenix or the flame?”. After a moment's thought, Harry provides the accepted answer: “A circle has no beginning.” This is Harry's first and only time inside the Ravenclaw Common Room. Upon entering, he observes the room's grand and intellectual atmosphere and, most importantly, the statue of Rowena Ravenclaw, which gives him a clear image of what the diadem looks like. His observation is interrupted by the arrival of Death Eater and professor Alecto Carrow, who was stationed there on Voldemort's orders. Upon seeing Harry, she summons the Dark Lord by touching her Dark Mark. Luna Lovegood stuns Alecto, and her brother, Amycus Carrow, arrives moments later. Enraged at the situation and his sister's state, Amycus suggests blaming the Ravenclaw students for the false alarm. When Minerva McGonagall arrives and intervenes, Amycus spits in her face. This act of disrespect provokes Harry to cast an unforgivable Cruciatus Curse on the Death Eater. This intense confrontation within the Ravenclaw Common Room serves as a critical prelude to the larger battle.