If you happen to be in Barcelona from November 26th to January 2nd and you want to see the Christmas lights you can either walk or take a bus.
I recommend you the Bus Turístic’s Barcelona Christmas tour, it goes around all the city so you can see the Christmas lights from another point of view and at the same time some Christmas traditions are explained while listening to some festive music.
Departure point: Plaça Catalunya
Departure times: 6pm and 8pm (no buses on December 25th and January 1st)
More info clicking here.