Waiting | Photo: Tom Walton
You can hire a "biketaxi" from Trixi.com (who call them "trixis") for various tours around the city [brochure] and if you're feeling a bit lazy, or Barcelona in August is just too hot, it's probably fun (we haven't actually tried them out). Look for them in the square outside the Cathedral [map].
Actually we think GoCars are more fun (and we have tried them — several times!) because with them you have to make the effort, not just sit there passively.
Driving a GoCar (a 50cc tricycle a bit like an open-top bubble car, if you remember them), rather than being peddled places, is a bit like being in a language class: you can't just sit there passively. In class (and after class, too), you've got to get actively involved in your own language learning…
>> You can also hire ordinary bikes from Trixi if you want to consume your own pedal power.