David J.
Yelp
Situated in the renovated port area, 10 minutes from the end of La Rambla, this claims to be one of Europe's largest aquariums. It makes for a good half day out for the kids if they are interested in wildlife, though it is undoubtedly expensive.
To start with, the aquarium is fairly traditional - lots of tanks, mostly well displayed, with captions in Catalan, Spanish and English, and a strong conservation theme. (There's no need to buy the guide-book, so save yourself EUR3). These cover the various different types of marine environments, from rocky coasts to sandy bottoms, in both temperate and tropical waters.
After about a dozen or so tanks, the main event is the huge sea tank which has two walk-through tunnels, equipped with moving walkways. These are seriously impressive (OK, not as big as the ones in Sydney, but as big as you'll find in Europe), with some large sharks, rays and a wide variety of other fish. For a separate fee you can dive with sharks, if you want to, at specified times.
After that, there are some more tanks, including a good one of octopuses and with the largest lobster I've ever seen in captivity - he/she was over a metre long, including the antennae.
On the next floor there's an activity area, with fresh water tanks (with piranhas), a large penguin tank with viewing platform, a lot of educational material, and a small but really interesting set of tanks containing jellyfish, spookily illuminated with UV light so their occupants glow in the dark. There is also a petting tank with rays and flatfish, though on our visit this was covered over. Also closed was the 'Explore!' area for kids, which contains more hands-on educational exhibits, like divers' costumes.
Practicalities
The main downer is the price - an eye-watering EUR17.50 for adults and EUR12.50 for children and EUR14.50 for people over 60 (2010 prices).
Most of the facility has level/wheelchair access (via lifts and some long ramps to start with) and there is a non-moving walkway through the large tanks if you prefer. There is a self-service locker area to leave coats etc (EUR1 charge). Photography is allowed, but not flash.
There's an expensive cafeteria and a good shop - lots of cuddly versions of the critters you've just seen, plus the usual assortment of fridge magnets, pens, key-rings and the like.
On our visit, it was blissfully uncrowded, but I'm told in high summer (and school holidays) it can get packed, so judge your timings carefully.