With all viewed inside the castle, you have to go back to the main entrance where the security guards are. Leaving from there take the path going down, passing through the necropolis, the church, and the tomb again. After the church, turn left and head down until you see another one. Once you are there, choose the left path once again and continue going down until you find a wooden door with a map of the castle near it. Go through the door and keep going until you see the Ferreira de Castro Alley on your left.