Ladies and gentleman, welcome to the Castle of Guimaraes. It was built in the 10th century and reconstructed in the 13th. Don´t worry, I won´t bother you with its history :) Follow the link if you are interested.
As you get close to it, you wonder why would you even try to scale those walls. I mean, I checked the place and this is the weakest point!
The inside is also impressive.
How can we break these magnificent defenses? Sit and wait. Seriously, that´s how sieges started. Stay far enough from the castle but force the citizens to stay inside until they run out of food. The best of it is that you don´t need to climb :)