While we're on the topic of shared spaces, hostels are another intriguing example. You're sharing a (small) sleeping area with (in my case) 3 people you've never met before, with whom you might or might not have a language in common.
So far, I've met 2 of my 3 "roommates." The first is a super-friendly Canadian from Montreal, with whom I chatted a bit (in French) soon after I arrived. The second roommate demonstrated the effects of body language and tone; I encountered him as I was coming out of the bathroom, and though we both said "Bonjour" it was clear he was not really interested in having more of a conversation than that. So it goes (I heard him speaking on the phone when I went back to the room a moment ago; I think it was Russian, but possibly another Slavic language).
So during my time in Paris so far, I wandered to the Sacré Coeur (quite close to the hostel), bought a sandwich and watched the sun setting over Paris. Nice. Then I wandered around for another hour or so (buying a Nutella crêpe along the way, which, to be honest, was a large part of the reason I decided to spend a night in Paris. It was a little disappointing, cause I got it near the super-touristy area around Sacré Coeur, but really, it's pretty hard to have a "bad" Nutella crêpe).
Tomorrow check-out is by 11 am, but my flight isn't until 3 pm; because of the bags I'll have, I will likely just find a park and eat a sandwich and a pastry. Mmm... Paris, que tu es delicieux!