The Diamond Castle is a beautiful text for children on Saint Teresa of Avila's work, Interior Castle. It introduces the beauty and splendor of the soul as imagined through the metaphor of the soul as a diamond castle. Many of St. Teresa's doctrines are introduced through additional castle symbolism, as defined by St. Teresa. Most especially, the "room of self-knowledge, identification of Christ as King of the Castle who dwells in the center room, praying to Christ as His Majesty, the importance of the Our Father prayer, the importance of keeping your castle clean so the Splendor of Christ's glory will shine out, and much more. The book includes a Ten Commandments pictorial, Glossary of terms used in the book, and key to the diamond castle symbols. An extensive reference of End Notes will assist catechists and academics who would like to explore the doctrines found in this first edition of The Diamond Castle. The book is meant to be first in a series of books which will teach children and even adults on major themes surrounding an interior life of grace as realized through union with His Majesty, Christ the King.