Hi there!
They will climb the Serra da Estrela twice in this Tour: on stage 3 (halfway through the stage on Saturday) and then on the penultimate day (stage 9) we'll have a moutaintop finish there(here we call the summit of the climb "Torre" like you mentioned). Well, we don't have many high moutains here, actually this is THE only real mountain we have, that's why we always use it...
On stage 4 we have the "Senhora da Graça" climb. It's our second most difficult climb, it's relatively short (8km) but it's steep (around 7,5%) and comes at the end of a very hilly stage, so it's traditionally a very important stage of the Tour. This year this stage comes early so it's not so decisive...
The organizers are trying to find other challenging climbs to include in the race and there are many steep climbs but nothing more than 3 ou 4 kms...
I recommend that you try the Senhora da Graça climb. Hope you enjoy your stay in our country.