The Interior Castle, or The Mansions, (Spanish: El Castillo Interior or Las Moradas) was written by St. Teresa of Avila, O.C.D., the Spanish Discalced Carmelite nun and famed mystic, in 1577 as a guide for spiritual development through service and prayer. Inspired by her vision of the soul as a crystal globe in the shape of a castle containing seven mansions, which she interpreted as the journey of faith through seven stages, ending with union with God.