You never know what you’ll find tucked into an old book.

In the 1960s, the British illustrator Pauline Baynes was working on a color map of Middle-earth, the land of wizards, elves and, of course, hobbits. While she was drafting the map, she worked closely with J.R.R. Tolkien, who sent her a copy of a map from a previous edition of Lord of the Rings, covered in notes revealing details of Middle-earth.

Baynes tucked that map into her copy of Tolkien’s trilogy, where it stayed for decades, until, just recently, it was found at Blackwell’s Rare Books, reports the Guardian.