Aqua Lusitana
The Oceanarium of Lisbon, with its 5,000,000 liter tank, is the largest indoor aquarium in Europe. Yes, even (!) bigger than Genoa aquarium. It reaches 7 meter deep, so that you can admire both pelagic and benthic species at the same time.
Here in the pictures a few of its 16,000 individuals. Can you spy the sunfish?