The second circle of walls can be found near the primary entrance of the castle. Instead of going straight to the ticket machines, you can access the gardens and the adjacent areas for free. You only have to show your ticket once you enter the actual castle. To find these walls, follow the marked trail to Casa da Guarda, which is indicated multiple times with wooden signs. Once you get there, with the Casa da Guarda on your left, you can see the extensive circle of walls.