the tower was ordered constructed by pedro de sem, chancellor under king d. afonso iv in the first half of the 14th century. before being integrated into the former-palácio dos terenas, this monument was part of the defensive wall ordered constructed in the first half of the 14th century, that also served as the centre of a pre-urban estate related to the medieval burg. it was a prestigious structure used by the monarch to affirm his presence to the city. by 1431, in the possession of marim do sem (sometimes known as martim d'océm), then-chancellor of king d. duarte (and great-grandson of pero de sem), who would eventually be buried in são domingos de santarém (his tomb was later transferred to the museum of são joão de alporão), was the estate of pero sem and its tower.