The Interior Castle was written by Teresa of Ávila (15151582), the Spanish Carmelite nun and famed mystic, in 1577, as a guide for spiritual development through service and prayer. The work was inspired by her vision of the soul as a diamond 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. her works form part of the literary canon of Christian mysticism and Christian meditation practice.