Written by Saint Teresa of Ávila, The Interior Castle is a classic work of Christian mysticism that describes the soul's journey toward divine union with God. St. Teresa uses the metaphor of a castle with seven mansions, representing stages of spiritual growth and intimacy with the Divine. She outlines the challenges and graces encountered at each stage, offering guidance on prayer, humility, and surrender to God's will. The work is a profound exploration of the inner life, emphasizing the transformative power of God's love and the ultimate goal of spiritual communion.