Like the church of Santa Susanna across Piazza San Bernardo, this church was designed by Carlo Maderno, but this one is best known for Bernini's sumptuous Baroque decoration of the Cappella Cornaro (Cornaro Chapel), on the left as you face the altar, where you'll find his interpretation of heavenly ecstasy in his statue of the Ecstasy of St. Theresa. Your eye is drawn effortlessly from the frescoes on the ceiling down to the marble figures of the angel and the swooning saint, to the earthly figures of the Cornaro family (who commissioned the chapel), to the two inlays of marble skeletons in the pavement, representing the hope and despair of souls in purgatory.
As evidenced in other works of the period, the theatricality of the chapel is the result of Bernini's masterly fusion of elements. This is one of the key examples of the mature Roman high Baroque. Bernini's audacious conceit was to model the chapel as a theater: Members of the Cornaro family—sculpted in colored marbles—watch from theater boxes as, center stage, the great moment of divine love is played out before them. The swooning saint's robes appear to be on fire, quivering with life, and the white marble group seems suspended in the heavens as golden rays illuminate the scene. An angel assists at the mystical moment of Theresa's vision as the saint abandons herself to the joys of heavenly love. Bernini represented this mystical experience in what, to modern eyes, may seem very earthly terms. Or, as the visiting dignitary President de Brosses put it in the 19th century, "If this is divine love, I know what it is." No matter what your reaction, you'll have to admit it's great theater.