While we were in Barcelona, Spain we either walked or rode the Barcelona Bus, which is a Hop on Hop off bus system. The buses are double decker with the top deck being open. The bus lines provide free headphones when you get on the bus so you can plug them in, select your language and listen as the narrator describe the sights you are passing by. We always sat on the top level of the bus and one of the funny sights I saw was at each bus stop there were what looked like hundreds of the blue earphones on the roof of the bus stop. Granted they are cheap ear phones but I brought mine home and later threw them out in the garbage.