This week I took the Transbordador Aeri, a cable car that goes across the port area, from Barceloneta to Montjuic. This is something we didn't do on our family trip here a couple of years ago. The views were great! Below you can see one of the towers in the distance and one of the cars. Then I hiked back to the station through Ravel, got home and soaked my foot in cold water - it was a bit too far of a walk for it. I forgot my camera so these are pictures taken with my iPod - not bad resolution, actually.
If you are going to do this, I would suggest doing it in the other direction: hike up to the Miramar lookout on Montjuic (there was a restaurant there with a great view) and do the route to Barceloneta. The waiting lines were much shorter that direction (in the afternoon in late October...).