Its non-stop street scene derives from the fact that nearly every one of its 20 arrondissements, or districts, has shops, offices, and apartments side by side and on top of each other.
Nearly every one of its 20 arrondissements are very quiet and peaceful. 
mnli hypothesis: Nearly every one of its 20 arrondissements are very quiet and peaceful.  premise: Its non-stop street scene derives from the fact that nearly every one of its 20 arrondissements, or districts, has shops, offices, and apartments side by side and on top of each other.