Interior Castles of the Soul St. Teresa of Ávila, born in 1515, was a Carmelite nun, mystic, and Doctor of the Church whose writings transformed Catholic spirituality. Through deep prayer and union with Christ, she taught that the soul is like a castle made of diamond or crystal, with many rooms leading toward the center—where God Himself dwells. Her masterpiece, The Interior Castle, remains one of the greatest guides to contemplative prayer and spiritual perfection. Teresa faced trials, illness