El Relámpago (CLOSED)
Time Out says
On both sides of C/Torrent de l'Olla there's a small emporium dedicated to the world of party decorations and costumes. But the beginnings of El Relámpago, established in the 1940s, had more to do with pyrotechnics (thus its name, which means Lightning). You'll find it all here, from table settings for Christmas to balloons and gift bags for birthdays, and Halloween/Carnaval costumes and accessories.