Although the castle itself survived earthquake of year 1755 (which destroyed almost whole city of Lisbon), the stability of walls was significantly decreased (and Christian chapel was severely damaged). In XIX the castle was once again rebuilt.
All this makes this place full of history.
What amazed me was that this location had been marked as "ruins" in the guidebook I used during my stay in Portugal and hadn't been amongst places necessary to visit in Sintra. For me, however, it is one of the most incredible castles I've ever seen. Built on the top of the mountain with incredible view from the towers and walls, with a great sense of history. The only drawback was wind. It was so strong that taking sharp photos was a real challenge and taking 3 bracketed photos for HDR processing was almost impossible :)