This is the oldest section in the palace, a fortified structure built to defend the surrounding lands. Renovated in the time of King Dinis and Isabel of Aragon (13th century), this Palace was a display of noble authority before the people. This authority belonged to the Queen to whom the King had granted the lands (and town) of Sintra. As the highest authority, the queens maintained their chambers in this zone of the Palace, which was the most inaccessible of all.

In the 17th century, the area came in for a different use. This became the prison of King Afonso VI, who was deposed by his brother. The king lived here in isolation and guarded over by 300 soldiers throughout nine years. The palace, a symbol of authority in times past but now obsolete, was now the prison space for a king who had been stripped of his royal authority. In the Chamber of Afonso VI, some of the oldest surviving ceramic flooring in the palace can be found (c. 1430-1440).