Eiffel Tower
Arc deTrode
Champs-Élysées
Louvre Museum
It's twenty-five euros and ninety cents for lifts all the way to the top. Children under four are free.
The Louvre is a very different experience than other museums, with an insane amount of pictures, detailed maps in many of the popular languages. This will most likely take you a day of you have nothing else to do and, the great thing is you will never get to it all and you'll need to come back. But if you do see all the paintings, they switch them out and there is more than 5,000 paintings in storage.