Some arrondissements are contiguous with old parishes, while others just provide a ramshackle administrative roof over largely disparate areas. For few arrondissements is this as true as for the 10th: which is central in the south (from its southernmost house front, you can see the Louvre), bourgeois-residential in the west (where it borders on the 9th) and fairly rough in its northwestern and southeastern corners (where it shades into the immigrant quarters of Barbès and Belleville respectively). Which easily makes the 10th the most diverse of all arrondissements: 5th Avenue, the Bronx and the Upper West Side all wrapped in one.
Tip: Spend your afternoon along the Canal St Martin, where Parisians love to go for a leisurely stroll on a sunny day, and, for a great evening out, walk over to the up-and-coming Chateau d'Eau neighborhood, famous for its numerous African hair salons (if a black man asks you if you want dreadlocks or braids, you know you have come to the right place).
Many of the rundown old bars and cafes in the area have been bought out by a young, artsy crowd who are turning the Rue des Petites Ecuries into the new "in" destination for a bohemian clientele. Certainly one to watch.