Built in late 16th century by the Master of the Works of the Convent, Francisco Lopes, during the priorship of Friar Adrião Mendes (1575-78), it was also the Chapter House in the time of Prince Henry (15th century). Work to unify the style was carried out in 1629-30 under the direction of Diogo Marques Lucas, architect to the Order of Christ. The vaulting decoration, dating from the time of the Spanish Philips displays a new Cross of Christ, the armillary sphere and the royal arms.