Savor freshly roasted chestnuts and sweet potatoes from una castanyera
The smell of fall in Barcelona is the slightly bitter smoke of chestnuts and sweet potatoes roasted over a fire by la castanyera, or the chestnut-roaster. For a few euros, she'll set you up with a warm sweet potato, or a paper cone full of chestnuts for a filling snack. Late September through Christmas, but especially during the month of October, it's easy to spot local children on the metro eating these traditional treats. That's because chestnuts and sweet potatoes are traditional foods in Catalonia for All Hallow's Eve and All Saints' Day.
During the Fall and Winter months, there's usually a castanyera set up on Ronda Universitat between Plaza Universitat and Raval, but when all else fails, follow your nose, there are castanyeras all around Barcelona.