Built in the 12th century and remodelled many times since, the castle now houses the Royal Military Academy. The grounds are normally closed, but on open days you can walk through the courtyards and see the chapel. The Spanjaardsgat watergate at the back of the castle is always accessible and worth a look.
The Nassaus -- ancestors of the Dutch royal family -- used Breda as their ancestral seat, and the castle was the centre of their power in the region for several centuries. The Compromise of Breda, a petition of nobility to the King of Spain that helped trigger the Dutch revolt, was signed here in 1566. In 1660, Charles II of England signed the Declaration of Breda in the castle, setting the terms for the Restoration of the English monarchy.