This is the Ridderzaal in The Hague where the Dutch queen addresses a joint session of the upper and lower houses of Parliament on the 3rd Tuesday in September. This day is called Prinsjesdag in Dutch, literally translated meaning Day of the prince.
The photo on the right shows the seat in the Ridderzaal where the Queen sits when reading the speech of the throne setting out the main features of government for the coming parliamentary session. To go to the Ridderzaal the Queen uses the golden carriage (see here on this picture I found on internet).
This year when I was home for lunch I was just in time to see the Queen getting into the carriage before making the ride through The Hague to the Ridderzaal. The ride in the golden carriage is so traditional for the 3rd Tuesday in September. Besides the golden carriage the hats of the female MPs are tradition too. They try to outdo each other with extavagant hats.