This is a must on any trip to Paris. Apart from the major sights, e.g, Arc de Triomphe, Eiffel Tower,
etc. it is good to marvel at the spectacular symmetry of the Place des Vosges. There are a couple of buildings that are not quite symmetrical and when you look closely they can can be found.
The other great thing about this part of Paris is exploring the streets of the Marais...a village within a city.