I never understood the location of Dumbledore's tomb. I thought it was at Hogwarts but the fact that Voldemort took the Elder Wand says differently. Where is his tomb? I would like an answer from the books. If that is unknown then the location based in the movie is fine (the in-universe location, not the real-life location).
All my personal Google searches gave me were the location that the scenes were shot in for the movies. So be careful if you Google search it.
It's next to the lake.
They were heading, as Harry saw when he stepped out onto the stone steps from the front doors, toward the lake. The warmth of the sun caressed his face as they followed Professor McGonagall in silence to the place where hundreds of chairs had been set out in rows. An aisle ran down the center of them: There was a marble table standing at the front, all chairs facing it. It was the most beautiful summer’s day. Harry Potter and the Half-Blood Prince, Chapter 30, The White Tomb.
The marble table here, once the ceremony is done, is the actual tomb. The merfolk are seen in attendance, so it's pretty much on the shore.
That would put it on the castle grounds, but well away from the castle itself. Easy enough to come in, take what he wanted, and leave.
To supplement Radhil's spot-on answer, the location of the tomb in the movies is, like the books, beside the Great Lake at Hogwarts. It's shown in Harry Potter and the Deathly Hallows: Part One when Voldemort breaks into Dumbeldore's tomb. You can watch a Youtube video of the clip here. The movies put the tomb on an island in the middle of the Great Lake. This is a departure from the books, where the tomb is on land beside the lake.
I never understood the location of Dumbledore's tomb. I thought it was at Hogwarts but the fact that Voldemort took the Elder Wand says differently.
The fact that Voldemort took the wand does not say differently. It is explicitly mentioned that Voldemort came to Hogwarts to retrieve the wand:
Voldemort was at the gates of Hogwarts; Harry could see him standing there, and see too the lamp bobbing in the pre-dawn coming closer and closer.
And now everything was cool and dark: The sun was barely visible over the horizon as he glided alongside Snape, up through the grounds toward the lake.
"I shall join you in the castle shortly," he said in his high, cold voice. "Leave me now."
And here it was, beside the lake, reflected in the dark waters. The white marble tomb, an unnecessary blot on the familiar landscape.
The spiderlike hand swooped and pulled the wand from Dumbledore's grasp, and as he took it, a shower of sparks flew from its tip, sparkling over the corpse of its last owner, ready to serve a new master at last.
