Built in the late 12C, shortly after the city had been captured by Alfonso Henriques, the cathedral (like those in Oporto, Coimbra and Evora) was also a formidable fortress. It has been frequently remodelled; the third chapel contains the 14C Gothic tombs of Lopo Fernandes Pacheco, comrade in arms of King Alfonso IV, and his wife. Fine treasury displaying magnificent religious artefacts.