Tintinburgh | Lisboa | Oceanario
Largest indoor aquarium in Europe, about 10m from Oriente station, the permanent exhibition is certainly worth the time and money. They have one big aquarium (1,000 m2) with large fish, that one can be viewed throughout the exhibition, so don't worry if there is too many people right at the entrance.
I was most impressed by octopuses and rays. It was quite challening to take photos, mostly because it was very dark space, but also because the glass is super thick and has a strange effects so it was only possible to take photos at right angle.