Matteo R.
Yelp
Largest aquarium in Europe, but I can't help feeling a bit disappointed. I first visited this aquarium decades ago, when it first opened. In 1992 the entire waterfront area of the Porto Antico was redone, with major works by Italian architect Renzo Piano. And the aquarium feels a bit outdated, like it had been built in 1992 and never really modernized. For an aquarium this size, there is a lot of dead space. This is not to say that there isn't a lot to see; it will take you 2-3h to visit the aquarium, depending on how much time you want to spend here.
Definitely buy tickets in advance; there is always a line, and this way you will be sure to get in. You will have the chance to pick the day and the time of your visit.
As there are different ticketing options, if you have young children my suggestion would be to get combo tickets for the aquarium and the City of Children, and skip the Biosphere and the panoramic lift. The biosphere is small[1], and it felt somehow disconnected with the aquarium experience. The panoramic elevator/Bigo was inexplicably closed between 12 noon and 5 pm on a Sunday; as we had morning tickets to the aquarium, we just couldn't make it to the panoramic elevator.
If you come here by train, the walk from Piazza Principe train station to the docks and the aquarium passes through some pretty derelict streets.
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[1] When we went, apart from some specific trees the only other things in there were some goldfish, a large parrot, some small birds, and a small glass cage with stick insects.