While having fun, a valuable lesson is learned in the sixth book of the "Crystal City" series. Carmella and Sam, both ten years old, and Max who is eight years old, are best friends who just happen to be cousins. With the help of an unlikely friend who can fly, they go up above the clouds to a city made of crystals. This is the sixth adventure the children have had in Crystal City. On this visit, Carmella's little three-year old sister, Clara, goes...