Caldas da Rainha was part of the ancient region Lusitania, inhabited by ancient Romans who took advantage of sulphurous waters sprouting in the region. Barbarian invasions destroyed most of the Roman-built baths. By the 13th century, the springs were known as "caldas de Óbidos", after the nearby town. At this time, a Benedictine order looked after the needs of the poor and cared for the lepers and rheumatics, who sought the healing waters. With the disbandment of the order by the 15th century, the area fell into disrepair.