I don't know if Saint Martin was cool, but at least a canal he left us.
It’s a magnificent 30 minute walk. If the weather is good, you’ll see (and should join) parisians having a pic nic by the canal. If it’s after dark and cold, most of them will be in Chez Prune, Le Comptoir Générale, or The cork and the cavan.
If you’re a movie buff, you’ll recognize the place where Amélie dropped her goldfish on her movie.
The best burritos in town (approved by a mexican friend of mine) are at El Nopal.
Keep walking all the way to the Canal de L'ourcq, all the Way to the Jaurés metro station. The beauty doesn’t stop here!
Canal Saint Martin, métro République (lines 3, 5, 8, 9, 11) or Jacques Bonsergent (line 5)