Palais de Chaillot, framed by the graceful arch of the Eiffel tower. Though I didn’t visit the Palais (see the menacing clouds), but it is definitely worth going to, if you have the time. It houses four museums and a theatre.
Another view of the world’s second ugliest building (The French make even ugliness worth watching. Nowhere else would people want to look at an eyesore. :D), framed by the delicate tracery of the tower’s arch.