Portugal doesn't have many extensive caves. Most are in the rolling hills between Coimbra and Setubal. We crossed a limestone range between Batalha and Fatima, although I wouldn't have recognised it as limestone if I hadn't been told. Photos taken from the coach window -
A show cave leaflet, Grutas de Mira de Aire , near Fatima-
There is a band of limestone in the Algarve, but I didn't go to this area.