Where is the defence against the dark arts classroom in Harry Potter and the Half-Blood Prince ds?

In "Harry Potter and the Half-Blood Prince," the Defence Against the Dark Arts classroom is located on the third floor of Hogwarts. It is situated near the Potions classroom, reflecting the close relationship between the two subjects in this book, especially with Professor Snape teaching Potions and Professor Horace Slughorn teaching Defense. The classroom is characterized by its dark, atmospheric decor, befitting the subject matter.