Inside Gryffindor Tower
Gryffindor Tower is the Hogwarts tower where the Gryffindor house Common Room is located. It is said to be one of the highest towers of the castle.
Gryffindor Tower is also mentioned in Harry Potter and the Philosopher's Stone, Chapter 17, Moment 3.
From the Story[]
"Members of Gryffindor house live and socialise in Gryffindor Tower while at Hogwarts. The Fat Lady (an oil painting of a large woman in a pink silk dress) guards the tower, which is where the boys and girls' dormitories and the common room are located. It is accessible to anyone who gives the correct password."