the astronomy classroom,

Astronomy is also the only field of study at Hogwarts which has a direct equivalent in the Muggle world. Known student activities include learning the names of stars, constellations and planets, as well as their location and movements, and describing the environments of planets and moons. Astronomy classes take place in the Astronomy Tower, the tallest tower in Hogwarts Castle, and include sky observation sessions with telescopes (each student has to buy one of his/her own).