The Enchanted Castle by Edith Nesbit

When you are young so many things are difficult to believe, and yet the dullest people will tell you that they are true -- such things, for instance, as that the earth goes round the sun, and that it is not flat but round. But the things that seem really likely, like fairytales and magic, are, so say the grownups, not true at all. Yet they are so easy to believe, especially when you see them happening. And, as I am always telling you, the most wonderful things happen to all sorts of people, only you never hear about them because the people think that no one will believe their stories, and so they don't tell them to anyone except me. And they tell me, because they know that I can believe anything.

When Jimmy had awakened the Sleeping Princess, and she had invited the three children to go with her to her palace and get something to eat, they all knew quite surely that they had come into a place of magic happenings. And they walked in a slow procession along the grass towards the castle. The Princess went first, and Kathleen carried her shining train; then came Jimmy, and Gerald came last. They were all quite sure that they had walked right into the middle of a fairytale, and they were the more ready to believe it because they were so tired and hungry. They were, in fact, so hungry and tired that they hardly noticed where they were going, or observed the beauties of the formal gardens through which the pink-silk Princess was leading them. They were in a sort of dream, from which they only partially awakened to find themselves in a big hail, with suits of armour and old flags round the walls, the skins of beasts on the floor, and heavy oak tables and benches ranged along it.