The Yellow Brick Road is a paved road that leads through L. Frank Baum's fictional world 'The Land of Oz' from the Oz books. It is one of the most well-known elements of the story, made iconic by the musical- and movie adaptations from 1939 and later.
In Beyond the Kingdoms, Alex, Conner, Mother Goose, Lester, Goldilocks, Jack and Red travel into the story and the Land of Oz in persuit of the Masked Man. When the Tin Woodman suggests they use the road, Alex gets very excited.
"Did you hear that, Conner?" Alex said. She had bright eyes and a huge smile. "He's taking us to the yellow brick road. The yellow brick road! My inner six-year-old self is flipping out!"
From the road, the friends go into Winkie Country.
In chapter 14, the road is referred to as "the most famous path in literature".