The medieval fence in Estremoz was built by King Afonso III (1245-1279) in 1261 and improved by his successors, mainly by his son D. Dinis (1279-1325). It has two opposite main doors (East-West axis): Porta do Sol or Frandina and Porta de Santarém.

The Porta da Frandina, facing east, is flanked by a semi-cylindrical tower, with a lowered portal on the outside and round on the inside. Above the arch, at the entrance, is placed a tombstone invoking the Immaculate Conception, patron saint of Portugal, as is usual in the reign of D. João IV (1640-1656), after the Restoration.