The Wardrobe

The wardrobe that took the pevensies to Narnia was a special one which was made from special wood.

When Digory went to Narnia and got the apple to protect Narnia, Aslan told him to take one to cure his mother. He planted a tree with the core of that apple and it grew up and was a magical one which started swaying when no wind was blowing. One day when Digory was older, the tree got blown down in a gale and Digory got a part of it made into the wardrobe. Even though he doesn't discover it's magical properties, someone else does.