Azkaban Prison had withstood the test of time, outliving both its creators and even those who remembered it's proud history. It had stood, once, as the gateway between two worlds; a place of history and lore keeping, a silent testimony to all which had come before it.
The veil between the worlds was thinnest here, allowing one to step seamlessly from one world and into another. Those responsible for its creation had long since passed from this life, their bones long since turned to dust. But their descendents had lived on, flourishing in a world that had not been the home of their forefathers, but had come to welcome them.
Few remained who could trace their lineage back to those few brave souls who had chosen to leave their homes, their world, behind. Of those few, none now remembered their lineage, nor that another world existed within reach.
Of those whose blood lines had survived the passage of years, many had been without the spark of magic within them, and their lines had become lost through the annals of time, war, and the 'muggle' world. Still more had intermarried until their own history was lost to them.
Among the latter, Hermione Granger was the first in over ten generations to exhibit such a strong gift for magic. She was the first, in close to 800 years, to visit those places filled with magic and history that her ancestors had once touched - though she was unaware of her lineage, of course. Too many marriages, outside blood and lost history existed between herself and those who had come before her.
But deep down, back through the ages and hidden within a generations-wide gap, existed the blood of one who had walked the roads between worlds; one who had bridged the gap from one world to another, and chosen to remain in a world as uncivilized as any untamed wilderness, and had left their mark upon it.
That mark was the fortress now known as Azkaban Prison. It had been over two thousand years since one of her blood had touched these ancient stones, and the magic left behind by its ancient creators reacted suddenly and strongly. It was sentient in a way, as sentient as Hogwarts School of Witchcraft and Wizardry had ever been. That sentience realized two things as Hermione's hands came into contact with the ancient stone walls that had lost so much of its honor - but none of it's history or magic.
FIrst, that one of the Old Blood had once again come within its ancient halls.
Second, that individual was in danger, frightened and without any to protect them.
The magic reacted in the only way it knew how; by drawing Hermione within, heedless of her gasp of alarm or her lack of knowledge as to not only her own lineage, but also what was happening to her - or why.