From C. S. Lewis, The Last Battle

About half an hour later - or it might have been half a hundred years later, for time there is not like time here - Lucy stood with her dear friend, her oldest Narnian friend, the Faun Tumnus, looking down over the wall of that garden, and seeing all Narnia spread out below. But when you looked down you found that this hill was much higher than you had thought: it sank down with shining cliffs, thousands of feet below them and trees in that lower world looked no bigger than grains of green salt. Then she turned inward again and stood with her back to the wall and looked at the garden.

"I see," she said at last, thoughtfully. "I see now. This garden is like the stable. It is far bigger inside than it was outside."

"Of course, Daughter of Eve," said the Faun. "The further up and the further in you go, the bigger everything gets. The inside is larger than the outside."

Lucy looked hard at the garden and saw that it was not really a garden but a whole world, with its own rivers and woods and sea and mountains. But they were not strange: she knew them all.

"I see," she said. "This is still Narnia, and more real and more beautiful then the Narnia down below, just as it was more real and more beautiful than the Narnia outside the stable door! I see... world within world, Narnia within Narnia..."

"Yes," said Mr Tumnus, "like an onion: except that as you go in and in, each circle is larger than the last."