Need recommendations for Portugal trip

[BrentC]

So we finally set a date to go to Portugal mainland and the Azores in June. I am trying to plan places and sites to visit. I have the Azores covered since my wife is from there but would like recommendations of places to visit on the mainland. We will be on the mainland for about 12 days. We will start in Lisbon and then travel north to Porto. From Porto we go to the islands for the rest of our trip.