Established in 1881, the Martins Sarmento Society is a cultural organization that boasts a diverse and valuable heritage. Among its notable possessions is the Martins Sarmento Archaeological Museum, a premier source of information on pre-Roman cultures in Portugal and one of the most significant museums dedicated to these cultures across Europe.

Located within the 14th-century Gothic cloister of the São Domingos church, the museum houses an impressive assortment of prehistoric and proto-historical archaeology, epigraphy, and numismatics. It also features a collection of contemporary art. Of particular importance is the Pedra Formosa (the Beautiful Stone), a funereal stele that Dr. Martins Sarmento brought to the museum in 1897.