Prehistoric sites with ditches are still rare in Portuguese Estremadura. So far we had notice of a small ditch in Mafra municipality (Gonçalvinhos), with an uncertain chronology. Recently a new site with a ditch was published (Pimenta et al, 2013): it is the site of Santa Sofia, in Vila Franca de Xira.
Under a complex occupation of the Late Bronze Age (and following historical periods) a ditch section was discovered and dated by radiocarbon and archaeological material from the Chalcolithic.
Ditch plan under later hut structures and ditch section (image taken from Pimenta et al, 2013)
Pimenta, J., Soares, A.M. e Mendes, H. (2013), "Cronologia absoluta para o povoado Pré-Romano de Santa Sofia (Vila Franca de Xira)", Cira_Arqueologia, II, p.181-194.