A very popular and cheap way to go around town is the municipal bicycle rental, Bicing. It’s easy: just take a bike from one of the stands (200 or so of those), and drop it on another stand when you reach your destination.
The same idea, which originally started here as far as I know, has been taken over by Paris and Washington DC.
PS: several people asked me fora a picture of the Torre Agbar at night. Well, it’s coming, friends! But not quite right now. Bit of patience required.