Another place I forgot to put on my list is the National Palace at Mafra. It is worth a couple of hours if you have the time on your drive from Obidos to Lisbon. All the other places I listed were north of Obidos and you can't possibly fit all those in, along with Coimbra, in a one day drive from Porto to Obidos. I enjoyed all of them and none of them were crowded but I had two nights in Obidos. I would have liked to visit the lines at Torres Vedras but couldn't fit that in. I would have skipped Fatima but that was important to my wife.