Some of the best sights in Paris can't be found by looking through a traveler's guidebook. Take courtyards for example. They're the garden-like spaces that are hidden behind apartment building doors and you have to know people who live here in order to find them. They're simple, and some visitors might not even give them a second thought, but I think they're incredibly charming and certainly worth a trip off the beaten path.
A lot of residences in Paris are connected by courtyards. You enter the area through one main door, pass through a little hallway into the open space, and from there you find access to a variety of buildings. There are often trees, plants, or flowers in the courtyards. Sometimes you can find a bench to relax on. They're a calm, welcoming retreat from the bustling city outside. I haven't met a courtyard I didn't like, and I'm thoroughly in love with this concept of interior hideaways; a concept that isn't highly publicized or accessible to the outside world. Maybe it's for the best. A city that knows how to keep its secrets is that much more fun to discover.