Versailles, the palace of kings. My last thing to do in Paris. A reasonable train trip out of town and joined the masses, although not as busy as I thought it might be.
The Palace is huge and opulent and grand. Some of the colours and decorations are garish, but I guess when you have all the money, you do as you want.
A rather large estate, took me about 4 hours to walk around and visit most of it. I think you could spend a whole day if not longer there to explore every inch, but I saw enough.