"The street ended in front of an enormous, intricately carved gate which led through a high white wall. The gate was open. Atreyu hobbled through it and came to a broad, gleaming-white stairway that seemed to end in the sky. He began to climb. Now and then he stopped to rest. Drops of his blood left a trail behind him. At length the stairway ended. Ahead of him lay a long gallery. He staggered ahead, clinging to the balustrade for support. Next he came to a courtyard that seemed to be full of waterfalls and fountains, but by then he couldn’t be sure of what he was seeing. He struggled forward as in a dream. He came to a second, smaller gate; then there was a long, narrow stairway, which took him to a garden where everything — trees, flowers, and animals — was carved from ivory. Crawling on all fours, he crossed several arched bridges without railings which led to a third gate, the smallest of all. He dragged himself through it on his belly and, slowly raising his eyes, saw a dome-shaped hall of gleaming-white ivory, and on top of it the Magnolia Pavilion. There was no path or stairway leading up to it. The traveler must get their by gift." -The Neverending Story
The Ivory Tower is the imperial capital of the fantasy world known as Fantasia (called Fantastica in Michael Ende's novel). It is also the official home of The Childlike Empress who rules all the land and it's inhabitants.
"But the Ivory Tower at the center still shimmered pure, immaculately white." -The Neverending Story
"A little later they flew over the outer edge of the “Labyrinth,” the maze of flower beds, hedges, and winding paths that surrounded the Ivory Tower on all sides." -The Neverending Story
In the Novel, the Ivory Tower is described as not being a tower, but actually a vast city bulit upwards. From a far distance it appears as a gleaming white tower, but it is infact an entire empire of people living within elaborate structures bulit on top of each other reaching up all the way up towards the clouds in the sky. At the very top is the courtyard that contains the home of the empress who lives in a beautiful white Magnolia flower made of intricately carved ivory.