The Royal Palace started its life in the mid 1600s and was the City Hall until King Louis Napoleon booted the City Council out and had the building converted into his palace in 1808. The palace is used by the government now for state functions and is open to the public when not in use. It is a very impressive building and considered (by a Dutch poet) to be the 8th wonder of the world when it was built. Maybe that goes a little far but it is an interesting building to visit.
The sculptures and decorations are drawn from mythology, and, along with the grandeur of the building, show just how highly the proud new republic thought of itself. Having achieved independence from Spain after 80 years of war, and having become the most important centre of global trade, the city fathers were showing off a little. Also on display is the French Empire furniture that King Louie commissioned.
Entrance costs 10 euros and the audio guide is included. Check out the link below to see if the palace is open on the day you want to visit.