Portugal has the largest oceanarium in Europe.

An excerpt from the article 37 facts about Portugal

It is located in the Park of Nations in Lisbon, which was created after the Expo'98 exhibition. The capacity of the oceanarium is 5000 cubic meters or over 5.000.000 liters of water. It is made up of a huge water reservoir with walls full of glass. It is surrounded by four two-story sections, each displaying the flora and fauna of a different ocean. You can admire the life and environment of the Pacific, Atlantic, Indian, and Arctic Oceans. The Lisbon Oceanarium has over 16.000 animals from 450 species.