The Portuguese Venice, although you don't need to pay 80€ for a single gondola ride! Aveiro is one of the regional capitals of Portugal and it another must see in the summer. Lots of traditional shops and make sure the try the local sweets Ovos Moles do Aveiro but don't get the ones with extra sugar (they are sweet enough without!).
Ever thought, "I really want to go the beach but really need to pay the old man upstairs a quick visit"? Well look no further than Chapel Senhor da Pedra, this is a bit of a unique concept but horses for courses and all that. From sun worshiping to son worshiping, two birds one stone / rock..... Anyhow, random or not it's a nice close stop off and worth having a look, there is a nice walk and small café which serves ice cream and cold drinks, and a selection of traditional snacks / food.
Now on a very serious note....wine. High on the list of "if you have time you should visit" goes a trip to the Douro valley. If you enjoy wine then I would highly recommend spending some time taking in the views and if you have chance you should go for a wine tasting experience and tour. We can both recommend some really nice vineyards if you are interested.
Keeping on the "if you like" theme, this time Bridges. If you like bridges you will love Porto (5 to see), you can even walk under one of them on the support arch <---- really great experience. Porto is the northern capital of Portugal and is the home of Porto Wine or Port. There is soo much you can do and see here, from wine caves visits to river tours on traditional Rabelos you will not be disappointed. We can advise in more detail where to go and which side of the river to go (you have Porto and Gaia - North and South sides of the River Douro).
"The best national park in Portugal!"......and coincidently only national park in Portugal is Gerês. It really is stunning and ideal for hiking, relaxing in a waterfall lagoon or just taking in the breathtaking views. I would advise taking some deet spray as there can be a lot of bitey bugs around there.
If you're into old palaces then the National Palace of Pena is Portugal's Balamory! With 12 million gallons of Dulux (estimated) and every colour known to the human race this place really is a spectacle! Just don't go here hungover as its a sensory overload!
With close links to the local football team (Feirense), Mr.Dogs hotdogs and 3 stray dogs that bark all through the night, this really is a must stop on your visit to Portugal. Although beware of the Cat; Snow does not like guests (contrary to how she looks in the pictures), loud noises or belly scratches. Free coffee though....