What is the importance of the caves in the mountain in the novel, The Dragonet Prophecy?

The caves serve as the home of the five dragonets for the first several years of their lives. The caves are located in the Sky Kingdom, though the dragonets are not certain about that until after Clay and Tsunami escape. There is a river running through the caves which allows Clay and Tsunami to swim from their usual place to listen in on conversations between the three dragons charged with raising them. There are separate caves for various activities, including sleeping and studying. The door is blocked by a boulder they cannot open from inside, but Clay and Tsunami manage to open it from outside, which sets the rest of the events in motion.