Like a number of other European cities (and we're not including Amsterdam's petty bike theft here), Barcelona's jumped on the urban bicycle rental bandwagon. Er, bike seat. Tandem?
Whatever, it's a great idea and seems to be extremely popular. Walk up, flash your swipe card and pick up a bike for as long as you need, then drop off at one of around 250 'stations'. Every thirty seconds sees another coast by.
Bonus points if you know the possibly clever way in which this is funded.