Location from harry-potter-half-blood-prince by
The tallest tower in Hogwarts — where Dumbledore dies.
Dumbledore and Harry return from the cave to find the Dark Mark over the Astronomy Tower. Dumbledore freezes Harry under the Invisibility Cloak. Draco arrives. Draco can't do it. Snape arrives. 'Severus... please.' The Killing Curse. Dumbledore falls from the tower.
The highest point of the castle, open to the sky. Battlements overlooking the grounds and the lake. Stars above.
Also known as: the Astronomy Tower