I need some travel recommendations

Hello guys, me and a friend of mine planning to visit Portugal around October. Personally I do not know much about Portugal, I only know Lisbon and Porto as I was thinking to apply for master's degree there few years ago. We want to experience the historical(and some natural)sights, cuisine, and culture in general.

We can spare around 7-10 days in total, and would prefer to use bus or train to move from one city to another. For this purpose, I would like to ask for your recommendations on which cities to visit that have serious importance on your "historical(and some natural)sights, cuisine, and culture in general" and we can experience them there. Based on your recommendations we will need to choose around 5 cities to visit as the time is quite limited. You can also tell a path like "Start with Lisbon go these places and then go to Porto and visit those places...".

Thanks in advance!